mASTerinG
EXPOSUR E
Per F eCT exPoSur e on Your diGiTA diGiTA l CA mer A
Andrew S. GibSon
Contents Introduction
3
Part One: Basic Concepts Measuring Light – Why Do Cameras Get Exposure Wrong? Film vs. Digital Using Raw The Exposure Triangle Thinking in Stops Exposure Values
5 6 9 16 20 27 29
Part Three: The Three Exposure Scenarios
73
Scenario One: The Brightness Range of the Scene Matches the Dynamic Range of the Camera’s Sensor
75
Scenario Two: The Brightness Range of the Scene is Less Than the Dynamic Range of the Camera’s Sensor
78
Part Two: Exposure And Your Camera Histograms The Mechanics of Exposure Exposure Modes Metering Modes Exposure Compensat Compensation ion
30 31 43 44 51 57
Scenario Three: The Brightness Brightness Range of the S cene is Greater Than the Dynamic Range of the Camera’s Sensor
83
Part Four: Exposure and Creativity
94
60 62 67 70 72
Bulb Exposures Neutral Density Filters Live View And Electron Electronic ic Viewfinders Manual Lens Attachments Incident Light Meters
2 | Mastering Exposure
Conclusion
Notice of rights All rights reserved. No part of this ebook may be reproduced or transmitted in any form by any means without the permission of the author. Copyright © 2017 Andrew S. Gibson
113
Fujifilm X-T1, 14mm, 1/125 @ f5.6, ISO 1600
IntRoDUCtIon
Exposure is a one of the fundamental photography photography skills. Good exposure is an essential if you want to create a technically good image. If you get the exposure wrong you’ll soon bump up against the limits of what you can fix in post-processing. There’s not much you can do about burnt out highlights or the lack of detail in underexposed shadows. Exposure should be simple. After all, it’s just a matter of making sure that the right amount of light hits the sensor. But, as most photographers know, that’s where it starts to gets complex. One reason that some photographers struggle is because exposure is different on digital cameras than film cameras. Your camera’s sensor is a different medium than film. It reacts to light differently. If, like me, you learned your craft on a film camera, it takes a while to realize that some of the fundamentals you always took for granted no longer apply.
Mastering Exposure | 3
This book will help you get to grips with the fundamental fundamental skill of exposure on digital cameras. As long as you have a camera that lets you set the aperture, shutter speed and ISO you have the tools required to master exposure. The book is divided into four sections. The first gives you a thorough grounding in the theory behind the techniques. The second explores the exposure modes and settings on your digital camera, so that you understand what each is for and when to use it. The third shows you how to put all the theory into practice to cope with any lighting situation. The fourth explores the links between creativity and exposure. There are a couple of terms I deliberately use in the book. The first, suggested exposure, describes the exposure settings settings that the camera selects in any automatic metering mode. This reading should always be treated as a suggestion, rather than fact. The camera can get it wrong and it’s up to you to override the camera’s suggested settings when necessary. The second is optimum exposure. I don’t like to use the term correct exposure as exposure is subjective. The optimum settings depend on your creative goals and whether you are using the JPEG or R aw format. Sound daunting? Don’t worry – exposure really is quite simple once you’ve mastered the basics!
4 | Mastering Exposure
Note: My experience is with Canon EOS and Fujifilm X series cameras. My main camera is the Fujifilm X-T1 (pictured above). I will refer to these occasionally throughout the book. The ideas and techniques apply to other makes of camera, with minor variations in terminology.
P a Rt o n e: b a sI C ConCePts
Before we can explore some of the more complex exposure related ideas and techniques it’s important to understand the basics. Some of these concepts are as old as photography itself. The relationship between aperture, shutter speed and ISO, for example, is as important now as it was 100 years ago. Other fundamentals are part of the digital age and relatively new. It’s important to understand the difference between JPEG and Raw files because the choice of which you are using influences the decisions you make about exposure. If you learned about exposure by using slide film, then you need to know why exposing for a Raw file is different. Equally, if you learned photography on a digital camera and would like to try using film it’s important to understand how film reacts to light differently. differently.
Mastering Exposure | 5
Canon EOS 5D Mark II, 85mm, 1/350 @ f2.8, ISO 1600
me ASuri nG liGhT – w h Y d o C A m e r A S GeT e xPoSure w r o n G ?
You may be wondering why your camera doesn’t arrive at the optimum exposure by itself every time. It’s a good question – after all, modern digital cameras are amazingly sophisticated machines. There are three key points you need to understand. understand. 1. No matter which metering mode you use, the camera is measuring the light reflected from the subject. The subject. The camera’s camera’s p processor rocessor works on the basis that a allll the reflected tones measured by the camera’s exposure sensor average out to mid-
Mastering Exposure | 6
Fujifilm X T1, 14mm, 1/125 @ f1.4, ISO 6400
gray (this is k nown as 18% gray). If the scene doesn’t average out to mid-gray, the exposure will be wrong. It takes human intelligence to recognize a non-standard
Left: I took this photo using Evaluative metering mode –
scene – the camera can’t do it.
the smartest metering mode on my EOS 5D Mark II. But it still got the exposure incorrect, underexposing by around two stops. This is because the camera is expecting that all the tones within the part of the image covered by the exposure sensor to average out to mid-gray. When they don’t, the camera gives an inaccurate reading. If the scene isn’t gray, it makes it gray by providing the exposure reading that achieves that.
It’s worth repeating as your camera’s electronic metering system is built on this basis. • Cameras measure light reflected from the subject. • You Yourr camera camera expects the average value of all the the tones measured by the exposure sensor to be mid-gray. • If the tones don’t average out to mid-gray, the camera will get get the exposure wrong. If you are photograph photographing ing a scene with a good mixture of dark tones, mid tones and light tones, that will probably average out to mid-gray. If the scene has a lot of light tones, it won’t. A good example is snow. The The camera doesn’t know that snow is meant to be white, it thinks it should be grey, and returns a suggested exposure reading that achieves that. The result? Grey snow and an underexposed photo (see the photo on the right for a similar example). If you’ve never seen this happen you can test it out by taking a photo of a white wall. Select any metering mode you like, the result will be more or less the same – gray. The same applies, applies, but in reve reverse, rse, for dark scenes. scenes. Try Try taking a photo of a bla black ck wall (if you can find one) and see what happens. The camera is expecting the wall to be
7 | Mastering Exposure
gray, not black, and again will return an exposure reading that achieves that. The result this time is an overexposed image. Maybe one day cameras will come with buttons labelled white and black so that you can tell your camera that it’s photographing something that isn’t gray. Until that day comes you need to override the camera’s settings yourself. The easiest way is by applying Exposure Compe Compensation. nsation. You’ll You’ll learn how later on in the book. 2. Calculating the optimum exposure is more difficult if the subject lacks contrast, or has too much of it. In it. In either case all the camera can do is measure what it sees and give a suggested reading. The camera will cope with low contrast scenes (although it may not give the best exposure reading, as we shall see later). But high contrast scenes, where the brightness range of the subject is greater than what the camera’s camera’s sensor can record, requires some decision making from the photographer.. Again, the intervention of human intelligence is required. photographer 3. The best exposure may differ depending on whether you are using the JPEG or Raw formats. If you are shooting JPEG, the aim is to record the tones within the scene as accurately as possible. If you are shooting with Raw, the aim is to put as much information into the file as possible, so that you can use it to create the best possible quality image when you process the file. The same scene could could potentially potentially require two different ex exposure posure settings depending on the file format used. This happens when the contrast of the scene is lower than what the camera’s sensor is capable of recording. The main reason behind this is th that at Raw files have greater bit depth depth than JPEG files – a concept that I’ll explore in more detail in the next section.
8 | Mastering Exposure
Left: Obtaining the correct exposure was a simple matter of increasing the exposure by around two stops. When you understand why your camera gets exposure wrong, it’s easy to compensate, especially when you have plenty of time to examine the result and take another photo with different settings.
Canon EOS 5D Mark II, 35mm, 1/125 @ f9.5, ISO 100
F i l m v S . d i G i TA l
If you’re an experienced film user you might be aware that the ideal exposure in any given setting may vary according to the type of film you’re you’re using. Even if you’ve never used film then please pay attention here. It’s quite interesting and will help you understand why I use the term optimum exposure, not correct exposure. Here’s how it works. Most photographers use one of three types of film – slide film (also called transparency film), color negative or black and white negative. Photos taken with slide film tend to look best when it is underexposed a little. That’s partly because the slide itself is the finished product. Not many photographers make prints from slides because the process is difficult and slide film lacks the dynamic range of color negative film. But slide film reproduces better in magazines and books, which is why it was the preferred medium for many professional photographers photographers..
Mastering Exposure | 9
Color negative film is the opposite. You need to overexpose, usually by at least a stop, to create a negative that is ideal for printing. Black and white film is different again. The usual workflow is to expose for the shadows and develop for the highlights. The optimum exposur exposure e is influenced your film developer and development technique technique.. The point is that that each type of film requires a different different exposure, exposure, even when u used sed to take a photo of the same scene in the same light. That’ That’ss one of the reasons why it’s impossible for your camera to calculate the optimum exposure every time. With film, that would only be possible if there were a way to let the camera know what type of film was loaded.
Exposure and digital cameras Building on what we’ve just learned, it’s entirely possible that the optimum exposure for a photo taken with a digital camera changes depending on whether you are using the JPEG or Raw format to save your photos. We’ll We’ll go into the reasons why in depth further on in the book, but for now I just want you to grasp this concept. Another thing that it’s important to understand is that your camera’s sensor doesn’t react to light the same way as film. I t’s a different medium, and a different way of making an image. Consequently, exposure with digital cameras requires a new approach. The biggest difference difference from film is the way that digital sensors record record light to tones nes and dark tones (highlights and shadows) within the scene.
10 | Mastering Exposure
Digital sensors have a linear response to light. If you double the amount of light that hits a specific pixel, that pixel doubles in brightness (until it reaches its point of maximum brightness). If you halve the amount of light the brightness of the pixel is also halved – again until you bump up against the point of minimum brightness. Film, however is different. The same principle holds true amongst the mid tones, but it’s different at either end of the brightness scale. If you double the amount of light reaching the film in the brightest parts of the scene, the film doesn’t record a tone that is twice as bright. Instead, it’s somewhat less than that. The result is that film holds highlight detail much better than digital sensors do. The same is true to a lesser extent with shadow detail. Another way to picture the linear nature of a digital sensor is to imagine that each pixel on the camera’s sensor is a well that fills up with light during the exposure. If one pixel receives twice as much light as another, it will be twice as full. When a well is full, that particular pixel can’t absorb any more light. When this happens over a large enough part of the sensor to be visible in the photo, the result is a white area without any textural detail. This is an overexposed, burned out or clipped highlight (all three terms mean the same thing). The non-linear nature nature of film means tthat hat it is less pro prone ne to over overexposed exposed highlights highlights.. You could say that the wells fill more slowly as they get full. The result is that film, when compared to digital, is much less prone to overexposure and preserves more highlight detail.
What does this mean in practice? Well, with digital cameras you have to be a lot more aware of what’s happening with your highlights than you do with film. It’s easier to overexpose and lose details in your highlights. This can influence the decisions you make about exposure. Does it matter if your photo has overexposed highlights? The short answer is probably. It’s subjective and a lot depends on the content of the photo itself. The problem is that overexposed highlights look kind of ugly in digital images. Some of the tones in adjacent areas may be pixelated, which doesn’t look very nice. Plus, if you really have overexposed parts of your photo, you can’t bring that lost detail back in Lightroom. Once gone, it’s lost forever. Preserving highlight detail is a challenge, especially when the brightness range of the subject is more than your camera’s sensor is capable of recording. I’ll lay out some practical strategies for dealing with this situation later.
11 | Mastering Exposure
Fujifilm X-T1, 35mm, 1/180 @ f2.8, ISO 6400
Above: According to Fujifilm its cameras have the ability to take photos that look more like they were taken with film than other digital c ameras do. Part of this is down to the way Fujifilm cameras cameras use color profiles. But some of it’s to do with the way that
Fujifilm cameras are calibrated to preserve more highlight detail. Perhaps the photo above, taken with a Fujifilm X-T1 camera, will help you decide if this could be true.
I took the photo below as an experiment to see how my digital camera would cope with clipped highlights. I set the camera to give a good exposure for the model, and as the background was much brighter (the sun is almost directly behind her) it was nearly completely burnt out. An enlargement of the same image (right) shows how the sensor has struggled to record detail in the highlights, and also that the transition between between the mid tones and the clipped highlights is very abrupt. The The result is a photo with very poor technical quality, and shows what can happen when you try and push the camera’s sensor beyond the limits of which it is capable.
12 | Mastering Exposure
Canon EOS 5D Mark II, 33mm, 1/180 @ f4.5, ISO 100
Noise Noise is often likened to grain, but they are not really the same thing. Grain is part of the structure of film. The larger grain in high ISO film help make it more sensitive to light. Low ISO films have grain too, although you might need a magnifying glass to see it. Film grain is often seen as aesthetically pleasing. Photographers Photographers like Robert Farber and Sarah Moon built their reputations by creating soft, dreamy images with high grain fast films. Noise, on the other hand, is a by product of using an electronic sensor to capture light. It’s an unwanted extra with a reputation for destroying detail and looking unpleasant. It’s not all bad though – noise is much less of a problem than it used to be thanks to advances in sensor technology. The ability to use use ISO settings of 6 6400 400 plus on the the latest camer cameras as and create images with very little noise is a tremendous benefit of digital cameras. When it comes to high ISO, digital cameras now deliver much higher quality images than film.
X-T1, 35mm, 1/125 @ f3.6, ISO 6400 Fujifilm X-T1,
There is a strong strong relationship betw between een exposure and and noise. If you underexpose an image, you’ll get more noise. If you then brighten it in Lightroom (to compensate for underexposing) you’ll make the noise even worse. And that’s why exposure with digital cameras can be so tricky. Overexpose and you clip the highlights. Underexpose and you lose shadow detail and increase noise levels. There’s not a lot of margin for error. To get the best out of your camera you need to get the exposure spot on.
13 | Mastering Exposure
Above: I took this photo at ISO 6400 on my Fujifilm X-T1. The enlargement (right) shows noise, especially in the shadows. This camera has relatively low noise levels at high ISO settings like this. Expect to see more high ISO noise on older cameras, and less noise on newer models.
Other differences There are a couple couple of other maj major or difference differencess between digital digital and film cameras cameras,, when it comes to exposure. Both are benefits. The first is the histogram. histogram. The histogram tells you whether whether you got an ac accurate curate exposure, and it does it instantly. This is invaluable. I remember shooting Kodachrome slide film, sending it off for processing and waiting a week for the slides to come back. I never really knew how accurate my exposure was until then. Now, if you make an error with the exposure, you can correct it and take another photo right away. The learning curve is much faster. If your subject is static, it gives you no excuse for not getting a well-exposed image. If your camera has Live View (and most do now) or an electronic viewfinder you may even be able to view a live histogram that updates in real time. You can use this to judge the correct exposure before you take a photo. The second is that that your camer camera a records all settings settings applied when you took the photo in the file’s metadata. This includes exposure related information such as aperture, shutter speed, ISO, the exposure mode and metering mode. With this knowledge you can analyze your photos and see the effects the settings have on the photo. This is a big improvement improvement ov over er film. When When I was learning phot photography ography shoot shooting ing slide film I had to record the exposure setting of each photo in a notebook, so I could match them to the slides when they returned from processing. I don’t miss those days at all!
14 | Mastering Exposure
Above: With Live View you can see a live histogram that lets you verify the exposure before you take a photo. This is useful when you have the camera mounted on a tripod and have plenty of time to think about what you’re doing, such as for a still life shoot like this one.
The Metadata panel in Lightroom’ Lightroom’s Library module shows a photo’s
Select EXIF from this menu to see the relevant camera data.
exposure related information as recorded by the camera.
The shutter speed and aperture used by the camera.
Exposure Compensation (if any) applied by the camera.
The ISO used by the camera. A record of whether the camera’s flash fired during the exposure. The metering mode used by the camera.
15 | Mastering Exposure
The exposure mode used by the camera.
Using Raw The difference difference between Raw and JPEG files is sum summed med up by the the following principle: Use Raw for quality, use JPEG for speed and convenience JPEG files are ready to use photo files generated by your camera according to the settings (including White Balance and color profile) selected in-camera. You can use them as is or edit them in programs like Lightroom, Photoshop Photoshop and Snapseed. A Raw file is not a photo. It’s a file that contains all the information collect collected ed by your camera’s sensor at the point of exposure. It needs to be processed using software like Lightroom and converted into a format (normally JPEG or TIFF) that other programs and websites can use. You can view Raw files on a camera or computer because they contain an embedded JPEG file to show a preview of what the photo looks like. One benefit of using Raw is that you can make the final decision on settings like White Balance and color profile when you develop the photo. All Raw conversion software gives you this option. But with JPEG you need to make these decisions when you take the photo, as you can’t change them afterwards. As cameras become more sophisticated, it seems the number of in- camera settings you can adjust multiplies. For example, on my Fujifilm cameras in addition to
16 | Mastering Exposure
Fujifilm X-T1, 35mm, 1/180 @ f5.0, ISO 1600
White Balance and camera profile I can adjust dynamic range, color, sharpness, highlight tone, shadow tone and noise reduction. When using JPEG, you need to 8 bit binary digit make decisions on all these settings (even if it’s just to leave them at the default value) before you take the photo. With Raw they are irrelevant – and you make your decisions in Lightroom. Photography.. You can read more about this way of working in my book Mastering Photography
Bit depth The biggest difference difference of all between the Raw Raw and JPEG file formats formats (and th the e one most relevant to the topic of exposure) is bit depth. Computers (and devices that are run by built-in computers such as digital SLRs) use the binary number system. Binary numbers contain two digits – 1 and 0 (the decimal system uses ten digits – 0 to 9). A single digit in a binary number is called a bit (shortened from binary digit).
128
64
32
16
8
4
2
1
1
0
1
1
0
0
0
1
128 + 32 + 16 + 1 = 177
This table shows how the binary digit numeric system works. Each numeral in the binary number represents a value. For example, the fourth numeral from the right has a value of eight. To calculate the figure represented by the binary number you count up the value of all the columns with a value of one. In this case, the binary number 10110001 equates to the number 177 in decimal notation.
tone toness p per er chan channe nell p per er pi pixe xell
tota totall p pos ossi sibl ble e tton ones es
An eight bit binary number looks like this: 10110001 (equal to the decimal number 177). The table on the opposite page shows how it works.
8 bit
256
16.78 million
12 bit
4,096
68.68 billion
The highest possible possible eight bit num number ber is 11111111 11111111 – or 255 in d decimal ecimal notatio notation. n.
14 bit
16,384
4.39 trillion
A JPEG file is an eight bit file. Each pixel contains eight bits of information for each of the three color channels (red, green and blue). This equates to a scale of 256 possible values (0-255). The three channels together give a theoretical total of 16,777,216 color tones (256 x 256 x 256) per pixel. Raw files, on the other hand, have either 12 bits or 14 bits of information per channel per pixel (depending on your camera’s specification). That’s a lot more
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This table shows how many tones for each of the three channels per pixel are recorded by 8, 12 and 14 bit files. Twelve and fourteen bit numbers are longer than eight bit ones and contain 12 and 14 digits respectively respectively,, allowing them to represent larger numbers.
information. The potential color tone value combinations run into the billions and trillions.
Raw
JPEG
When your camera converts the information captured by the sensor into a JPEG file, it compresses it into an eight bit file. If you use the Raw format, all the information captured by the sensor is retained, ready for you to process yourself. The experts say the human eye can perceive around ten million or so colors, so clearly JPEG files are more than capable of recording all the colors you could possibly need. But what JPEG files can’t match is the level of detail that Raw files contain in the lightest and darkest regions of the photo – the shadows and highlights. You can pull this extra detail out in post-processing, and lighten or darken the image while losing less detail in these important areas. For these reasons alone, most professional or serious photographers use the Raw format. Some people use JPEG files because of the convenience and speed. They may be wedding photographers photographers (who take a large volume of photos that would take too long to process in the Raw format), sports photographers (who need JPEG files that can be sent to the picture desk as soon as they are taken) or just photographers that don’t like to use computers much. But, you should only use JPEG if you have a compelling reason to do so. Raw gives you a better quality image that you can do much more with in Lightroom, every time.
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Above: I made these two abstract photos on the same evening. One is a Raw file from a Fujifilm camera (left) and the other is a JPEG (right). Take a look at the next page to see the difference that file format makes in Lightroom.
JPEG
Raw
Above: This is what happens to the JPEG file when I push the Shadows slider in Lightroom to +100. The JPEG file doesn’t hold much detail in the shadows. Lightroom can’t bring out what isn’t there.
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Above: This photo shows you the effect setting Shadows to +100 has on the Raw file. It holds much more shadow detail. Lightroom can pull that information out when you Develop the photo.
The e xPoSur e TriAnGle
What do the following settings have in common? 1/250 second, f4, ISO 200 1/8 second, f16, ISO 100 The answer is that that both give you the same e exposure. xposure. They let the same same quantity of light reach the sensor. But the look of the photos will be completely different. The first settings give you shallow depth of field and a sharp image that freezes action. You could use them if you were photographing a sports event, or making a portrait. The second settings settings give you lots of depth o off field. But the slow shutter sp speed eed turns anything that’s moving into a blur. You could use these settings if you were taking a landscape photo and had the camera mounted on a tripod.
Mastering Exposure | 20
Canon EOS 5D Mark II, 85mm, 1/180 @ f2.8, ISO 400
The combination combination of ISO, aperture and shutter shutter speed is called the exposure triangle.
Sometimes you may be forced to use a certain aperture. For example, if you are
These are the only only three variables tthat hat you can adjust adjust when it co comes mes exposure exposure.. Every photo uses a combinatio combination n of these three settings.
shooting at dusk, with a hand-held camera, you will need to use a wide aperture to get a shutter speed fast enough to prevent camera shake.
Even if you use Exposure Compen Compensation sation to make the image lighter or darker the camera is only adjusting one or more of these variables.
Or, if you are shooting in bright sunlight, you may be forced to use a narrow aperture even with the lowest ISO and fastest shutter speed settings.
That’s why exposure a That’s appears ppears so deceptively deceptively simple. There are only three settings tto o adjust. The complexity complexity lies in arriving at those three settings.
Another consideration is image quality, which is always best somewhere in the middle of aperture range of your lens. Generally speaking, the sharpest aperture settings are f8 or f11. These are good apertures to use if sharpness is a priority and the depth of field suits your creative intent.
Part of the complexity is because exposure is not just a matter of calculating the optimum exposure. You have to pay attention to the creative side of things as well. Here are the considerations for each of the settings that collectively form the exposure triangle.
But don’t be afraid to use the extreme aperture settings of your lens if needs be – image quality isn’t the only consideration. I often shoot at wide apertures because I like the narrow depth of field. That creative effect is more important to me than squeezing more sharpness from the lens by using f8 or f11.
Aperture Aperture controls depth of field. A wide aperture such as f2.8 gives you a narrow
Shutter speed
depth of field. I use f2.8 a lot when taking portraits to blur the background behind the model.
You need to decide whether you want to freeze motion (in which case you’ll need a shutter speed of around 1/250 second or faster), show a sharp image with a little bit of motion (around 1/30 to 1/250 second depending on focal length) or to show motion blur (around 1/30 second or slower).
A small aperture gives you more depth of field. Apertures of f8 to f16 are commonly used in landscape photography to make sure the entire scene’s in focus. The choice of aperture aperture is driven by how how whether you want want part of the sce scene ne in focus, or all of it.
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Practical considerations also come into play. If you are hand-holding the camera and require a sharp image, you’ll need a shutter speed fast enough to prevent camera shake. If you have a tripod you can use whatever shutter speed you want.
ISO Generally speaking, if image quality is your priority you need to keep your ISO setting as low as possible. However,, with the latest digital cameras you can use However a high ISO and still see little noise in the final image. It seems that every year new cameras are announced which push the boundaries of what can be achieved at high ISOs back a little further. It’s worthwhile taking a series of photos at all the ISO settings on your camera to see where your tolerance level is. It’s a personal choice, but once you’ve decided the highest ISO that you are comfortable shooting at in terms of image quality, you know to keep under that level when you can. Sometimes, such as if you need a fast shutter speed or a narrow aperture, you are forced to raise the ISO to compensate.. This depends on the light levels, but when compensate this happens you need to decide which has the highest priority – the required aperture or shutter speed or the ISO. This will help you decide which setting to adjust.
Canon EOS 5D Mark II, 85mm, 1/350 @ f2.8, ISO 200
Above: My main concern with this portrait was to set a wide aperture to blur the background. I selected f2.8, rather than the lens’s f1.8 maximum aperture, as this aperture setting gives a good balance between bokeh and face sharpness in portraits. With ISO set to 200 a shutter speed of 1/350 second gave the optimum exposure.
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All exposure settings are comprised of a combination of ISO, shutter speed and aperture (below). This is called the exposure triangle. The diagram on the right shows the settings that make up the triangle, and the effect that changing them makes to your photos. S S E L
2 f 8 . 2 f
Shutter speed is the length of time that the camera’s shutter is open during the exposure. On most EOS cameras this is anything from 1/8000 second to 30 seconds.
The aperture is a diaphragm within the lens. It closes down when you take a photo to let a specific quantity of light enter the lens. The smaller the aperture number, the larger the hole.
D L I E F F O H T P E D 8 f
ISO describes the sensitivity of the camera’s sensor to light. The higher the ISO, the more sensitive the sensor.
1 1 f
6 . 5 f
1 / 3 0
1 / 1 5
E ( 1 S X / 8 H P U O T S T U 1 / E R R E 4 S T P I E M E E D
G N I ) N E E R P U T O R S E N P E A L (
M O V E M E N T
)
E R O M
1 6 f 2 2 f
1 / 2
M O R E
1 2
SENSOR SENSITIVITY (ISO)
100
200
LESS
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f 4
L E S S
1 / 6 0
400
800
NOISE
16 16 0 0
4 3200
MORE
6400
1/90 second @ f1.4, ISO 1600
1/3 second @ f1.4, ISO 50
Above: In this photo I played with the idea of using a wide aperture to throw a recognisable landmark – the Hong Kong skyline – out of focus. To do so I
Above: This photo was taken moments after the one on the previous page, but in this case I set a slow shutter speed of 1/3 second and moved the camera
focused on the edge of a nearby building and set the aperture to f1.4.
during the exposure to create an abstract, blurred image (this technique is called Intentional Intentional Camera Movement or ICM for shor t on photo sharing websites like Flickr) . I kept the wide aperture and set a low ISO to achieve the desired shutter speed.
I also wanted a shutter speed of 1/90 second to ensure that the image was free from camera shake. With these two variables decided, I set the camera to Aperture Priority mode and raised the ISO to 1600 to give the desired shutter speed. I could have taken a tripod and used a lower ISO or smaller aperture. But I didn’t as I’d decided ahead of time to get creative and use wide apertures and a high ISO.
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This is an example of two different approaches approaches to selecting the most appropriate combination of aperture, shutter speed and ISO. The best combination depends on your creative goals as well as ambient light levels.
Right: I made this photo one evening in near darkness. I was attracted to the reflection of the street lamp in the bodywork of the vintage car. I had to set the ISO to 6400, the highest setting available on my camera, because of the low light. I also needed to set the shutter speed to 1/60 second to avoid camera shake. At those settings, an aperture of f1.4 gave the optimum exposure.
Fujifilm X-Pro 1, 35mm, 1/60 @ f1.4, ISO 6400
25 | Mastering Exposure
Right: For this landscape photo I set the ISO to 200, the lowest on my camera. I also needed an aperture of f8 to render the entire scene sharp. The shutter speed that gave the optimum exposure was 42 seconds. In many ways the shutter speed setting was the most important because I wanted to use a long shutter speed to blur the water. Working at dusk is an advantage because you can set the aperture and ISO, then gradually use longer shutter speeds as the light fades. It gives you the opportunity to take advantage of the fading light and experiment with different shutter speeds.
Fujifilm X-Pro 1, 18mm, 42 seconds @ f8, ISO 200
26 | Mastering Exposure
Thinking in Stops Take a close look at the the following sequ sequence ence of shutter speed speed settings. 1/8000, 1/4000, 1/2000, 1/1000, 1/500, 1/250... What comes next? It’s easy to work out once you know how shutter speeds work. Look closely and you’ll see that each setting is approximately double the length of the previous one. That means that the next number in the sequence is 1/125 second. This is followed by 1/60 second and continues until you reach 30 seconds, the longest shutter speed (excluding Bulb) on most cameras. Each progression along this sequence of numbers is called a stop. If you change the shutter speed from 1/250 second to 1/125 second, for example, it is said that you have increased the exposure by a stop. It simply means that the amount of light reaching the sensor has doubled. If you go the other way and increase the shutter speed to 1/500 second from 1/250 second, you have decreased the exposure by a stop. Half as much light reaches the sensor at 1/500 second than 1/250 second.
27 | Mastering Exposure
The same applies to the aperture a and nd ISO settings settings.. This is the the aperture setting sequence. The widest apertures are found on prime lenses (the widest aperture on zoom lenses tends to be f2.8 or f4). f1.0, f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22 As you progress from left to right, each number represents a stop. If you change the aperture from f8 to f11, you are decreasing the exposure by a stop (halving the amount of light that enters through the lens). If you change it from f8 to f5.6, you are increasing the exposure by a stop, and doubling the amount of light entering the lens. The sequence of of ISO numbers is tthis. his. 50, 100, 200, 400, 800, 1600, 3200, 6400, 12800, 25600, 51200, 102400, 204800 Note that for all of these there are intermediate settings at 1/3 or 1/2 stop intervals as well as the main ones listed above. They exist so that you can make fine adjustments to exposure.
The reason that cameras use stops is to make it easy to understand the effects
Right: I took this photo with an aperture of f8, a shutter speed of 1/160 second and an ISO
of changing ISO, aperture and shutter speed.
of 200. Imagine for a moment that that after I had taken the camera I looked at the histogram and realized the photo was underexposed by around a stop. How do you compensate for that? You have three choices.
For example, let’s say the camera suggests an exposure of 1/125 second at f5.6 and ISO 400. When you check the camera’s histogram you realize that the image was underexposed by around a stop (you’ll learn how to read a histogram in the next chapter). That means you need to increase exposure by a stop. There are three ways you could do this. 1. Change the shutter speed to 1/60 second. 2. Change the aperture to f4. 3. Change the ISO to 800. The choice is yours. yours. Y You ou could also change more than of the settings by using the intermediate values (although that would get a little complicated), or use the Exposure Compensation function instead (covered later).
28 | Mastering Exposure
First, you could set the ISO to 400. You need have to consider that increasing ISO may also increase noise, but to be honest on most modern cameras you’re not going to see a difference between ISO 200 and 400. Second, you could open the aperture by a stop, giving a setting of f5.6. The consideration here is depth of field, which you would have less of. Third, you could change the shutter speed to 1/80 second. As I used a 50mm lens to take the photo this shouldn’t give a problem with camera shake. The decision is yours. The advantage of working in stops is that you get to decide which setting to change.
Canon EOS 40D, 50mm, 1/160 @ f8, ISO 200
Exposure values Another term that you may come across from time to time is Exposure Value (EV). For most photographers EV is of academic interest only. However, some older light meters give light readings in terms of EV only, so if you have one of those you will need to understand how to convert an EV value to aperture, shutter speed and ISO settings. If the ambient light has an Exposure Value of 0, it means that a shutter speed of 1 second at f1.0 and ISO 100 is required to give the correct exposure. Exposure values increase in stops, just like aperture, shutter speed and ISO settings. An EV of 1 means that the light is twice as bright (as an EV of 0) therefore you need a shutter speed of 1/2 second at f1.0 and ISO 100 to achieve the correct exposure. The table on the the right shows th the e relationship between between Exposure Values and exposure settings at ISO 100. The exposure settings are only a guide – think back to the example I mentioned earlier of slide film and color negative film. Color negative film needs to be overexposed by a stop or more compared to slide film to give the best result. The same applies to Raw and JPEG formats – there are situations where, because I shoot in Raw, I’ve overexposed by one or two stops compared to what I would do with a JPEG file. That means that the settings in the table, based on Exposure Values, are just a suggestion – a starting point. They only take into account the level of ambient light, and not the contrast of the scene, therefore their value is limited.
29 | Mastering Exposure
You’ll also find that EV gets a mention in your camera’s specifications (found at the back of the instruction manual). The metering range of the camera is given as an Exposure Value range. This means that the camera’s exposure meter is accurate, as long as the ambient brightness levels fall within the given EV range. This is nothing to be concerned about – you would have to be shooting in either near darkness or extremely bright light to fall outside your camera’s metering range.
EV
f1.0
f 1. 4
f2
f2.8
f4
f5. 6
f8
f 11
f 16
f 22
0
1
2
4
8
15
30
60
120
240
480
1
1/2
1
2
4
8
15
30
60
120
240
2
1/4
1/2
1
2
4
8
15
30
60
120
3
1/8
1/4
1/2
1
2
4
8
15
30
60
4
1/15
1/8
1/4
1/2
1
2
4
8
15
30
5
1/30
1/15
1/8
1/4
1/2
1
2
4
8
15
1/60
1/30
1/15
1/8
1 /4
1 /2
–
–
–
10 20
1/1000 1/500 1/250 1/125
–
–
–
–
1/80 1/8000 00 1/40 1/4000 00 1/20 1/2000 00
This table shows the relationship between EV values and shutter speed and aperture. These are the recommended settings to give the correct exposure at each Exposure Value and the camera’s ISO set to 100.
PaRt two: ex PosUR e anD yo U R C a m e R a
Your camera has a number of tools designed to help you with exposure. As we have already seen exposure is theoretically simple. All you have to do is decide which aperture, shutter speed and ISO to use. But getting there can be surprisingly complex. Your camera has several exposure and metering modes. It’s up to you to select the most appropriate modes for the situation you are in. There is no perfect way of metering light, so your camera gives you a choice of several imperfect methods. Luckily it’s a relatively easy decision to make, as you will understand by the end of this chapter.
30 | Mastering Exposure
Mastering Exposure | 30
Fujifilm X T1, T1, 56mm, 1/1100 @ f1.6, ISO 1600
hiSToGrAmS
Histograms are the reason why it’s so much easier to calculate the optimum exposure with a digital camera than a film camera. Histograms tell you whether your photo is underexposed, or overexposed, how much contrast it has and whether you have any overexpose overexposed d highlights. By the end of this chapter you will know how to view your camera’s histogram and, more importantly, interpret the information information it gives you. This important skill is the foundation of everything else you will learn in this book about exposure. Most (not all) cameras show you two different types of histogram – the luminance histogram and three color histograms. Each tells you something different.
Mastering Exposure | 31
Canon EOS Rebel XT, 18mm, 1/125 @ f11, ISO 100
The luminance histogram The luminance histogram histogram is a whit white e graph that represents the ttonal onal values in your image on a scale of zero to 255. The histogram histogram is a bar graph, and appears as a continuous shape because there are no gaps between the bars. The left hand side of the histogram represents th the e darkest tones tones,, and the right hand side the lightest tones. It starts at zero (pure black) and finishes at 255 (pure white). The mid tones of the photo are found, naturally enough, in the middle of the histogram. You may read that a perfect histogram peaks in the centre of the graph and slopes downwards to meet either end. In practice, there is no such thing as a perfect histogram – each one is different depending depending on the tones within the image. The luminance histogram histogram also ind indicates icates the amount amount of contrast contrast within the scene. A narrow graph indicates that the photo doesn’t have much contrast. You You’ll ’ll see this type of histogram if you take a photo on a foggy day, for example. A wide graph indicates that there is more contrast in the scene. It takes a while to learn to read a histogram and understand what it’s telling you. On the next few pages are some examples to help.
32 | Mastering Exposure
Above: Luminance Luminance and color histograms displayed on the back of a Canon EOS camera. On this camera, you have to press the INFO. button twice to see the luminance histogram, and once more to see the color histograms. Every camera is different, so check your manual to learn how to view the histogram on your model.
The histogram on this page is an enlargement of a histogram taken from the back of a Canon EOS camera (see right). The luminance histogram histogram show showss tonal values only and contains no color information. To To make it easier to see the tones in the photo I’ve included another version with the color saturation set to zero – a simple black and white conversion. The histogram on the back of tthis his particular is camera is divided into five zones. Each zone is labelled on the diagram. The histogram of this particular image doesn’t stretch stretch all the way across the graph. There are no dark shadows, and no bright highlights. The photo is mostly comprised of mid tones. This is a very regular histogram histogram – if there there is such a thing. You’ll see some different histograms on the next few pages.
33 | Mastering Exposure
s e n o t t s e k r a d
s l e x i p f o r e b m u n
0
s e n o t k r a d
s e n o t d i m
s e n o t t h g i l
pixel brightness
s e n o t t s e t h g i l
255
This histogram (above) shows shows that the ma majority jority of tones in the the photo on the left are bright ones. This makes sense when you look at the photo – you can see the bright sky takes up most of the frame. There are no dark shadows in the image, and the darkest fifth of the histogram is completely empty of pixels. The hazy lighting conditions mean that the photo has very little contrast. I developed the photo without increasing contrast so you can see exactly how it was captured by the camera. As you can see there are no dark tones – just mid tones and highlights.
34 | Mastering Exposure
Canon EOS 5D Mark II, 85mm, 1/250 @ f13, ISO 100
I took this photo with a Fujifilm X-T1 camera. I can’t show a screenshot of the display of this camera, but I can show you the luminance histogram from Photoshop (below). It’s It’s not exactly the same as you would see on the camera, but it’s close enough. The histogram for this photo shows that the the exposure is very very good. T There here are no overexposed highlights or shadows that lack detail. It could be argued that the photo would benefit from a little more exposure. This is a technique called exposing to the right that’s covered later in the book.
Fujifilm X-T1, 14mm, 1/125 @ f4.5, ISO 1600
Small gap on right side of histogram
35 | Mastering Exposure
Above: The photo without any extra developing, just as the camera recorded it. Did you notice the gap on the right side of the histogram? It’s there because the photo doesn’t have any bright highlights.
This interesting histogram (tak (taken en from Photo Photoshop, shop, belo below) w) shows the d difference ifference in brightness between the sky and the foreground. Th The e sky is overexposed and the Raw file has lost much of the detail there. The foreground, foreground, if anything, is slightly underexposed.. The large gap on the right of the histogram indicates that there underexposed are no highlight tones. The photo transitions abruptly from the mid tones in the foreground to the overexposed highlights in the sky.
The gap that indicates there are no bright highlights in the photo apart from the overexposed sky.
Fujifilm X-T1, 14mm, 1/125 @ f9, ISO 1600
The peak in the graph here indicates the photo has clipped shadows. In this case it indicates the foreground is underexposed.
36 | Mastering Exposure
The peak in the graph here indicates the photo has overexposed highlights
Above: The photo without any extra developing, just as the camera recorded it.
The large gap on the right of this photo’ photo’s histogram, combined combined with tthe he way the graph is cut off on the left shows that the photo is underexposed. The result is that there are shadow areas in the photo that lack detail. This is confirmed when we look at the photo itself (right). There is very little detail under the eaves and in the dark wooden door.
The large cut off peak in the graph here indicates that the photo has lots of clipped
This gap in the graph indicates that there are no bright highlights in the
shadows.
photo.
37 | Mastering Exposure
Fujifilm X-T1, 14mm, 1/125 @ f13, ISO 200
The Highlight Alert The Highlight Alert warns you if there are any clipped highlights highlights in your image image..
The photo below is
It takes the form of blinking black patches when you play back an overexposed image on the LCD screen.
mostly made up of dark tones. This is confirmed by the spike on the left-hand side of the histogram (right).
The Highlight Alert is a kind of early warning system to alert you to poor exposure exposure.. The histogram and Highlight Alert wo work rk together. together. The histogram histogram tells yyou ou that you have clipped highlights in the image, and the Highlight Alert tells you where they are. Some cameras let you turn the Highlight Alert off so that it doesn’t distract you when you play back photos. If you do this remember to turn it back on when exposure is critical, or you may accidentally overexpose overexpose photos without realizing it.
Specular highlights There is one type of highlight that w will ill almost inevitably inevitably be clipped in yo your ur photos and there’s very little you can do about it (apart from shooting in softer light). Specular highlights occur when you are photographin photographing g highly reflective sur faces, such as polished metal and water, water, especially in bright sun. Specular highlights are usually small and not worth worrying about. The Highlight Alert indicates their size.
38 | Mastering Exposure
The Highlight Alert shows a specular highlight on the metal lion.
Canon EOS 5D Mark II, 85mm, 1/250 @ f5.6, ISO 400
What the Highlight Alert really tells you The histogram on this page (again (again,, taken from P Photoshop) hotoshop) shows that this photo of a man working in a traditional knife making factory in northern Spain has clipped highlights. The Highlight Alert confirms confirms that there are clipped highlights and shows what parts of the photo are affected. The photo was was made indoors in a dim room, room, so naturally (as we would expect) the windows are overexposed. So is the light bulb hanging from the ceiling.
The large peak on the left indicates that the photo (shown right) has clipped shadows. The high contrast nature of the light and the dark interior of the room means this is to be expected. It doesn’t, in this case, indicate a problem with exposure.
What does this say about exposure? Not a lot, except to confirm the obvious – that the brightness range of the scene is greater than the camera’s sensor can handle. But more importantly the Highlight Alert is a sign that you need to make a decision. You might decide to do nothing (as I did) and accept there is little you can do about the clipped highlights. Or, you could look for a way to frame the scene that excludes the windows and light bulb and make the problem disappear that way. The point is that that the histogram histogram and Highlight Alert are just information – it’s up to you to interpret them and decide what action, if any, to take.
39 | Mastering Exposure
The small peak in the histogram tells us that the photo has clipped highlights. The Highlight Alert, shown on the right, shows you where the clipped highlights are. Fujifilm X-T1, X-T1, 35mm, 1/180 @ f4, ISO 3200
The color histograms Color histograms are similar to luminance histograms, except that the horizontal axis shows color saturation, not tonal values. Each photo has three color histograms (as well as a luminance histogram); one for each of the three color channels (red, green and blue). Color histograms are a guide to the color balance within the image. If the image is dominated by a blue object, for example, then the blue histogram will show more tones than the red and green ones. Color histograms also indicate if there are any oversaturated oversaturated colors in the image. If one of the color channels is oversaturated, you may lose some textural detail in the photo. This doesn’t doesn’t matter in the case of something like blue sk y, where there is no detail, but it may matter with a subject like flowers, which have both strong colors and texture. If the color histograms indicate that one of the color channels is clipped, you can take another photo with half a stop or so less exposure to see if that fixes it (see the example on the next page). Most cameras can display the color histograms as well as the luminance histogram. But not all do. The exceptions tend to be older cameras, but some new cameras can’t display color histograms either. Fujifilm cameras are a good example. To be honest with you I don’t miss the color histogram and have never had a problem with oversaturated colors on my Fujifilm cameras.
40 | Mastering Exposure
The color histograms displayed alongside the luminance histogram on the display from a Canon EOS camera. Each of the three color channels (red, green and blue) are displayed separately. For this particular image, the color histograms confirm that there are more red tones than green or blue ones.
The luminance histogram histogram of this photo of a red red flower (above) (above) shows that there are no bright highlights – there are no pixels in the right hand fifth of the graph. This suggests that we can increase the exposure without clipping highlights. Go to the color histograms though and we see a different story. The red histogram is spread all the way across the graph. This is not surprising as red is the dominant color. But it also tells us that if we increase exposure, we are at risk of clipping some highlights in the red channel. The histograms histograms below show what what happened when when I increased expo exposure sure by a stop stop.. The luminance histogram histogram (and Highlight Alert) indicat indicate e that there is no clipping in the image. But the color histograms show that there is clipping in the red channel,
41 | Mastering Exposure
and indicate that some detail may have been lost. In practice, it doesn’t seem to make much difference. I processed both photos seen here so they have the same brightness level and can barely see the difference between them at 100% magnification. There There is slightly less detail in the highlights on the red petals in the second image – but you have to look hard to see it. If you are photographi photographing ng a brightly colored object, such as this flower, you should check the color histogram (if your camera has it) as well as the luminance histogram to see if there is any clipping in any of the color channels. If there is, it doesn’t hurt to take another photo with slightly less exposure, just in case you did lose some detail in the affected channel.
Where histograms come from The luminance histogram, histogram, along with the phot photo o that you se see e on your camera camera’s ’s LCD LCD screen, is generated from a JPEG file. This is true regardless of which format you are shooting in – if you are using Raw the camera embeds a thumbnail JPEG file within the Raw file that it uses to generate the histograms and the image you see on the LCD screen. The JPEG file used used to generat generate e the histogram is processed usi using ng the Wh White ite Balance, exposure and color profile values set when you took the photo. Even if you are using Raw and intend to process the file afterwards, in order to get the most accurate histogram possible you should enter the White Balance and color profile settings that most closely match the post-process post-processing ing treatment you intend to use. If you are using Raw, there is probably more detail in the highlights and shadows than the histogram indicates, thanks to the extra information stored in Raw files. This means that highlights that are clipped, according to the histogram or Highlight Alert, may not be so in practice. This doesn’t mean you can get careless
I took these photos on a Canon EOS camera to illustrate what happens to the histogram when you increase contrast in-camera. The first image (left) was taken with the contrast set to the default setting of zero. There are no clipped highlights and the camera’s sensor easily captured the entire brightness
with exposure – you should still pay attention to what you are doing and make sure that the right hand side of the histogram doesn’t extend beyond the edge of the graph.
range.
When you’re you’re using Raw the contrast of the JPEG file used to generate the histogram is determined by the contrast settings of the camera and the selected color profile. If you increase the contrast the histogram may show highlights or shadows to be clipped, where they wouldn’t be if contrast was left at the default. Because of this it is best not to increase contrast in-camera as it may result in inaccurate histograms.
42 | Mastering Exposure
The second photo (right) was taken with the contrast set to +4 (the highest setting). The The histogram is wider and some of the highlights are clipped (the area affected is shown by the Highlight Alert). If I had used the JPEG format those highlights would indeed be clipped and the histogram would be accurate. But as I was using Raw the histogram is misleading and can’t be relied on to accurately accurately show the tonal distribution of the photo.
The m eChAni CS oF exPoSure
Despite the huge variety of cameras available today today,, and recent advances in digital technology,, the tools your camera has for dealing with exposure are broadly technology the same no matter which camera you own. Evaluative metering becomes more sophisticated as cameras evolve, and newer cameras can measure the exposure from the camera’s sensor, enabling Live View, electronic viewfinders and Movie mode, but other than that the tools on even the newest professional specification digital SLR haven’t changed much in the last twenty years. In this section you will learn how to use your camera’s tools to obtain the optimum exposure for your photos.
Mastering Exposure | 43
Fujifilm X T1, 35mm, 1/180 @ f7.1, ISO 3200
Exposure modes Virtually every digital SLR or mirrorless camera has the following exposure modes. • • • •
Programmed Auto (P) Aperture Priority (A or Av) Shutter Priority (S or Tv) Manual (M)
They are the most most useful exposu exposure re modes on the the camera as they g give ive you full control over all the camera settings.
Right: The Mode Dial from the Nikon D7200. The four most useful exposure modes (manual, Aperture Priority, Shutter Priority and Programmed Auto) are separated from the camera’s automatic exposure modes by a white line.
Most cameras also give you at least one fully automatic exposure mode, where the camera makes all the decisions for you. These exposure modes not only set the aperture, shutter speed and ISO, but may also set things like White Balance, color profile and file format without giving you any way to override the selected settings. You may not even be able to use Exposure Compensation.. These exposure modes are desi designed gned for photographers photographers who don’t don’t know h how ow to use the Programmed Auto, Aperture Priority, Shutter Priority or Manual modes. They are a simple way of letting such photographers use some of the more advanced capabilities of a digital SLR camera.
If you are in the habit of using any of them, then stop right now and switch to the Programmed Auto, Aperture Priority, Shutter Priority or Manual modes. That’s where you’ll learn how to take control of your camera to create the images that you want to make.
Fully automatic exposure modes should be avoided by creative photographers who know what aperture, shutter speed or ISO they want to set and why.
It’s also the only place where you can make exposure decisions yourself instead of leaving it to the camera.
44 | Mastering Exposure
Aperture Priority (A or Av) & Shutter Priority (S or Tv) Good photographers try and use aperture and shutter speed creatively. Because of this you will often prioritize two of the exposure triangle settings over the other one. For example, if you are taking a landscape photo you may want to set a narrow aperture (to ensure the entire scene is in focus) and a low ISO, and let the camera work out the shutter speed. You can do this with Aperture Priority. In this mode, you set the aperture and ISO, and the camera sets the shutter speed required to expose the image correctly according to the camera’s built-in light meter. You can indirectly affect the shutter speed by changing ISO. On the other hand, a sports photographer would probably prioritize shutter speed and ISO over aperture. Shutter Priority is the mode for this. In Shutter Priority, you set the shutter speed and ISO, and the camera sets the aperture. You can indirectly affect the aperture by changing the ISO setting. Canon EOS 5D Mark II, 85mm, 1/250 @ f2.5, ISO 400
If you are in Shutter Priority mode and the maximum aperture of the lens isn’t wide enough to give the correct exposure at the selected ISO, the camera will give you some kind of indication in the viewfinder to let you know (check your manual for the details). You You need to set a slower shutter speed or a higher ISO. Note: Most camera makers use the letters A to stand for Aperture Priority and S for Shutter Priority. Canon and Pentax are different. They use Av (Aperture value) for Aperture Priority and Tv (Time value) for Shutter Priority.
45 | Mastering Exposure
Above: I set the aperture of my 85mm lens to f2.5 to make this portrait. I used Aperture Priority mode to do so as this allowed me to set the aperture that I wanted to use.
Right: For street photography I prefer to set my camera’s shutter speed to 1/250 or 1/500 second to freeze motion. Shutter Priority is the ideal mode for this. You can then control the aperture indirectly by adjusting ISO. For this photo I set the shutter speed to 1/180 second. The movement of the man’s arms is frozen by the camera, but the rolling pin, the outside surface of which is moving much faster, is blurred.
Fujifilm X-T1, 35mm, 1/180 @ f5.6, ISO 3200
46 | Mastering Exposure
Programmed Auto (P) In Programmed Auto mode, you select the ISO and the camera selects aperture and shutter speed according to the metered light levels. Unlike fully automatic modes modes,, you retain full control over all the camera settings. You could think of Programmed Auto mode as ISO priority. You set the ISO and the camera sets aperture and shutter speed. It’s the ideal exposure mode to use when you would rather concentrate on making images than worrying about the precise aperture and shutter speed settings. Note: Programm Programmed ed Auto is the term used by Nikon for this exposure mode. Canon, Fujifilm and Sigma use Program AE; Sony uses Program Auto; Olympus uses Program Shooting and Pentax uses Hyper-program.
Program Shift You can override the camera’s selected aperture and shutter speed setting with Program Shift. Check your manual for the details, but this is usually activated by the dial near the shutter button, so you can see the settings in the viewfinder without taking the camera from your eye. With Program Shift, the camera changes the aperture and shutter speeds simultaneously to retain the correct exposure. This means you are not locked in into to the settings settings selected by the camera and can override them when you need to. Note: The term Program Shift is used by most manufacturers except Nikon, who Note: The uses the term Flexible Program.
47 | Mastering Exposure
Canon EOS 5D Mark II, 40mm, 1/125 @ f8, ISO 800
Above: This is the type of photo that could easily be taken in Programmed AE mode. The camera will set a shutter speed fast enough to prevent camera shake and the aperture will take care of itself. If you don’t like the settings the camera selects you can change them using Program Shift.
Manual mode(M) In Manual mode you set the aperture, shutter speed and ISO by yourself. The
Aperture Priority mode as an example. If you set the aperture to f8 and the ISO to
viewfinder indicates whether the exposure is correct (according to the camera’s meter) but apart from that you’re on your own.
400 the camera can only set one variable, the shutter speed. But with Auto ISO the camera can change both shutter speed and ISO. Most cameras let you set both the lower and upper limits of ISO. So you could, for example, tell the camera not to use an ISO higher than 800 to help ensure good image quality.
Manual mode is useful in situations where you have the time to determine the optimum exposure and the light levels aren’t changing. Once you’ve decide on the exposure settings to use, you just lock them into the camera and shoot. The reason that that photograph photographers ers do this is becau because se the camera’s camera’s meter meter can be surprisingly fickle. If you’re taking portraits of a person wearing light clothes against a dark background, for example, the exposure reading will constantly change as you change viewpoint and framing, depending on the balance of light and dark tones within the frame. As long as light levels are constant, using Manual mode saves you dealing with that. If the light levels are changeable, on the other hand (perhaps the sun is going in and out behind clouds) then you are better off using Aperture Priority, Shutter Priority or Programmed Auto modes.
In Aperture Priority you set aperture and the camera selects shutter speed and ISO. In Shutter Priority you set shutter speed and the camera selects aperture and ISO. In Programmed Auto the camera sets aperture, shutter speed and ISO. You can even set Auto ISO in Manual mode. In this instance you set the aperture and shutter speed yourself, and the camera sets the ISO according to its light meter (check your manual for the details as it varies between camera models). It turns Manual mode into a semi-automatic mode, and it’s not something I’d ever do myself, but I’m sure somebody somewhere has found a use for it!
Auto ISO With a film camera, the ISO is determined by the film loaded into the camera. The only way to change it mid-roll mid-roll is to change the the film. But with d digital igital ISO has become a variable and you can change it whenever you like. This has given rise to to a new function called called Auto ISO. ISO. The examples examples given previously in the book assume that the ISO, once set, doesn’t change. Take
48 | Mastering Exposure
The camera’s exposure meter is still active in Manual mode. As you adjust ISO, shutter speed and aperture the bottom marker indicates whether the exposure at the selected settings is correct according to the camera’s meter. In this example, the marker shows that the image is underexposed by one stop.
Right: This is the type of photo where it is advantageous to use Manual mode. If you use an automatic mode, the reading will vary according to the way in which you frame the scene and the placement of the girl wearing white. This means that the exposure reading given by the camera is constantly changing, when (as long as the light levels are constant) the optimum exposure settings remain the same regardless of composition.
Canon EOS 5D Mark II, 17mm, 1/125 @ f4, ISO 800
49 | Mastering Exposure
I like to use Manual mode when I do long exposure landscape photography. I start by setting the camera to Aperture Priority mode and dialling in the required aperture and ISO. I then take a meter reading (by pressing the shutter button half-way) and transfer the shutter speed that the camera gives me along with the aperture and ISO into Manual mode. Then I take a test exposure, and adjust the shutter speed if necessary according to what the histogram tells me. At this point I’m ready to go. As the sun sets (I normally take this type of photo at dusk) and the histogram starts creeping to the left from frame to frame I can lengthen the shutter speed (or open the aperture or raise the ISO) half a stop at a time to keep the exposure correct. I keep doing this until the light fades away completely.
50 | Mastering Exposure
Fujifilm X-Pro 1, 18mm, 85 seconds @ f8, ISO 200
Metering modes Most cameras offer at least two of the following metering modes; Evaluative, Partial, Center-weighted Center-weighted Average and Spot metering. Why do cameras offer more than one exposure mode? The main reason is that there is no per fect solution to the problem of calculating an automatic exposure exposure reading using reflected light. Even Evaluative metering, the camera’s most advanced metering mode, is still fooled by scenes that are lighter or darker than average. Each metering mode is just grappling with the problem in a different way. Center-weighted Center-weigh ted Average and Spot metering existed long before Evaluative metering, and some photographers may feel more comfortable using them. They are simple modes and their behavior is easy to predict when you understand how they work. Spot metering has its own specific uses (I’ll explore those in a bit), but it’s not as useful with digital cameras as it was with film.
Limitations of exposure modes Imagine that you are taking a photo of someone and the sun is setting behind them. Your Your subject is in the shade and the sk y is much brighter. brighter. You can either expose correctly for the bright sk y, rendering the person as a silhouette, or expose correctly for the person, and risk a bright sky that may contain overexposed highlights.
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This is where you you run up against tthe he limitations o off what your cam camera’ era’s metering system can do. It doesn’t matter which metering mode you use, the camera doesn’t know your goals. It can only meter the light reflecting off the subject and make a decision based on that. It’s up to you to apply the information the camera’s meter is giving you and use it to work out the most appropriate exposure to produce the result you want. In this hypothetical situation it’s all down to what you want to achieve. Do you want a silhouette or do you want to see the person in your photo? You may even want both, in which case you could expose for the sky and use a portable flash or a reflector to bounce light back onto your sitter. Maybe in the future cameras will be smart enough to give us better advice than they do now, but for the moment we have to think for ourselves. Fortunately, the instant feedback provided by the histogram and the camera’s LCD screen let us see straight away whether our chosen settings worked. The instant feedback makes challenging lighting situations much easier to deal with than they were in the past. Let’ Let’ss take a closer look at how each exposure mode works.
Center-weighted Average metering The meter reading reading is taken from the entire scene and weighted towards th the e center of the viewfinder on the basis that the subject will be in the center of the frame. If the subject is off-center (as it often is) you need to do a little extra work. Point the center of the viewfinder at the subject, push the shutter button halfway to focus and lock in the exposure reading, then recompose and press the shutter button down all the way to take the photo.
Partial metering The exposure reading reading is taken fro from m an area in the center of the fra frame me smaller than used for Center-weighted metering but larger than used for Spot metering. Partial metering is useful if your subject is backlit, or the background is unusually light or dark. You can take a reading from your subject and use that reading as a starting point for your exposure settings.
Above: These diagrams show the coverage of Centre-weighted metering (left) and Partial metering (right) on a Canon EOS camera.
Canon and Sigma are the only manufacturers who add Partial metering to their cameras. Sigma calls it Center Area metering.
Centre-weighted metering takes most of the frame into account, but weights the exposure towards the reading taken from the central portion.
Spot metering
Partial metering takes a reading from a small area in the centre of the frame. No other part of the frame is measured.
Spot metering returns an exposure reading from the circle at the centre of your viewfinder. It is like Partial metering, but uses a smaller area. It’s an interesting exercise to switch your camera to Spot metering mode and point the centre circle at different objects on a bright sunny day. You You will see how much contrast there is in the scene and how different objects return different readings depending on how much light they reflect back at the camera.
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Spot metering is a useful tool in assessing a scene on film cameras, but is less useful on digital cameras. The accuracy of Evaluative metering and the instant feedback provided by the histogram give a better way of arriving at the optimum exposure. But there’s there’s no harm in experimenting with Spot metering to see if it ’s a useful tool for you. Here are some suggested ways of using it. 1. Use Spot metering to measure the brightest tone in the scene. The scene. The suggested exposure reading will render that bright tone as a mid tone, so you need to dial in around one and a half to two stops extra exposure to make it a light tone. Check the histogram afterwards to make sure that the highlights aren’t clipped. This can be a shortcut shortcut to determ determining ining the best exposure exposure settings. 2. Take a spot reading from an 18% gray card placed in the scene and use that reading to calculate exposure. This exposure. This method works if the brightness range of the scene matches the dynamic range that your camera’s camera’s sensor is capable of recording. It doesn’t work well in low contrast scenes when you want to use the expose to the right technique (covered later in the book). These techniques techniques work well with the the camera set to to Manual mode mode,, as you can ad adjust just aperture, shutter speed and ISO to arrive at the optimum exposure settings.
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Fujifilm X-T1, 35mm, 1/180 @ f5.6, ISO 800
Above: This is the type of scene that photographers used Center-weighted Average metering for before Evaluative metering was added to cameras. The idea is that taking the exposure reading from the center of the frame reduces the likelihood that a bright sky will make the camera underexpose the photo.
Evaluative metering Evaluative metering is the most sophisticated metering mode on your camera. Evaluative metering was developed to make the task of arriving at an accurate suggested reading easier, and less prone to errors, than when using Centerweighted Average metering. Evaluative metering divides the viewfinder into zones, each one giving a separate reading. The camera analyzes the readings and calculates the exposure. The number of zones zones depends o on n which camera you you have. Some Some cameras have have hundreds, some have less. Check your camera’s manual for details. Evaluative metering comes in useful when using E-TTL (electronic through the lens) portable flash units (Canon and Nikon have the most advanced portable flash systems) as it works with the flash to calculate the required exposure. Evaluative metering may be your camera’s most sophisticated metering mode but it’s still prone to the same errors as all the others. The suggested exposure is influenced by scenes with lots of light tones, or lots of dark tones, or that are backlit, or where the sky occupies most of the frame. It may be slightly more accurate than the others, but still requires the photographer to step in and override the settings to achieve the optimum exposure. Note: Canon and Sigma use the term Evaluative metering. Nikon uses matrix metering, Sony and Pentax use multi segment metering, Fujifilm uses multi metering and Olympus uses digital ESP metering.
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Above: This diagram shows the Evaluative metering pattern of the Canon EOS 80D. The viewfinder is divided into 63 zones for metering purposes. The metered area excludes the edges of the frame.
Testing Evaluative metering I printed out some test patterns to demonstrate how a change in the quantities of light and dark tones influence the camera’s exposure meter. I photographed each pattern in bright sunlight. The amou amount nt of light falling on each piece of paper is the same, therefore we know that the optimum exposure is the same for each. But based on our knowledge of how exposure meters work, we can predict that the camera’s meter will give an incorrect reading for some of the patterns. You can see the results on the next page.
The camera should give the same exposure reading for each of these patterns. That’s because the black and white tones in the first two images, when averaged out over the frame, create the same mid-grey tone that the third image has.
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The camera’s meter should give an incorrect reading for these two patterns, as the majority of the tones are either black (left) or white (right).
Nearly perfect. There are two The histogram for this patt pattern ern is There are two spikes in this histogram – one in the centre spikes in the histogram – one on nearly identical to the previous the left that corresponds with one. This is to be expected as the corresponding to the grey rectangle and the other on the the black squares and one on total area of white and black is right representing the white the right that corresponds with the same. border. the white ones. The histogram is more or less central. Despite the high contrast of the pattern the sensor doesn’t lose any detail in either the shadows or highlights.
The camera’s camera’s e exposure xposure mete meterr has increased the exposure settings in order to render the average of all the tones in the pattern grey. The result is overexposure overexposure – the highlights are clipped and the blacks are grey, not black. The two spikes in the histogram represent the black and white tones respectively. The spike for the black tones is much further to the right than in the histograms for the first two patterns.
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The camera’s camera’s meter meter has decrea decreased sed exposure to give the settings that render the average of the tones in the pattern mid-grey. The two spikes correspond to the black squares and white tones respectively.. The larger spike is respectively almost central when it should be in the right hand fifth.
Exposure Compensation As we’ve already seen your camera gets exposure wrong in many situations. When this happens there are two ways to override the camera’ camera’ss suggested meter reading.
Exposure Compensation Compensation is measured in stops. Most cameras let you apply between two and five stops negative or positive Exposure Compensation.
1. Use Manual mode. Increase mode. Increase or decrease exposure by adjusting the ISO, aperture or shutter speed settings.
It is unlikely that you will have to apply plus or minus five stops Exposure Compensation Compensatio n to compensate for errors in the camera’ camera’ss metering (two stops is usually the maximum required). But the extra range comes in useful if you want to take a sequence of photos with different exposures to create a High Dynamic Range (HDR) image.
2. Use an automatic exposure mode (i.e. Programmed Auto, Aperture Priority or Shutter Priority). Apply Exposure Compensation to increase or decrease the exposure. The purpose of Exposure Exposure Co Compensation mpensation is very very simple. There There are two wa ways ys to use it. 1. Tell the camera to let more light reach the sensor than the exposure meter recommends. If you are photographing photographing a white dog against a white wall, for instance, you know that the camera’s meter is going to recommend an exposure that underexposes the scene. You can use Exposure Compensation to tell it to apply two extra stops of exposure, so that the photo is correctly exposed. 2. Tell the camera to let less light reach the sensor than the exposure meter recommends. An example of when you might do this is when part of the scene is overexposed and you would like to avoid clipped highlights.
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Above: On most cameras Exposure Compensation is displayed using the scale in the centre of the viewfinder display. If the pointer is in the middle, no Exposure Compensation has been applied (top). The pointer moves to indicate the amount of Exposure Compensation Compensation applied (middle and bottom).
How Exposure Compensation works The exact way Exposure Exposure Com Compensation pensation works depends on which exposure mo mode de you are using. Most cameras work the following way – check your camera’s manual if you see anything unusual happening. Shutter Priority: The Priority: The camera adjusts adjusts exposure by by changing the ap aperture. erture. You may come up against the limit of the aperture range. For example, if the maximum aperture of your lens is f4, and the camera has already selected this setting, if you use Exposure Compensation to increase exposure, the camera can’t open the aperture any wider. If this happens, you’ll see some sort of indication in the viewfinder to let you know that you can’t achieve the required exposure at these settings. If Auto ISO is enabled, the camera may change the ISO instead. Aperture Priority: The Priority: The camera adjusts adjusts exposure by by changing the shu shutter tter speed. If you come up against either end of the shutter speed range (ie 30 seconds or 1/8000 second on most cameras) the viewfinder indicates that the required exposure can’t be achieved. If Auto ISO is enabled, the camera will change the ISO instead. Fujifilm X-T1, 18mm, 1/125 @ f8, ISO 200
Programmed Auto: The Auto: The camera may may change either shutter shutter speed or ap aperture erture to apply the required Exposure Compensation. Above: This This is the sort of lighting situation where you could use Exposure Compensation to compensate for underexposure caused by the strong backlighting. Alternatively Alternatively you could use Manual mode. The choice is yours.
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Exposure Compensation or manual mode? My experience of using two camera systems (Canon and Fujifilm) has made me realize that the mechanics of the camera matter just as much as the lighting situation when it comes to deciding the best way to override the camera’s settings. For example, within the Canon EOS range the more expensive cameras have a Quick Control dial on the back which you can use to dial in Exposure Compensation easily without taking your eye from the viewfinder. Applying Exposure Compensation Compensatio n is straightforward. It is harder to use Manual mode, because you have to press several buttons and turn several dials to adjust the aperture, shutter speed and ISO. It’s easiest to use Manual modewhen the camera is on a tripod, and Exposure Compensation when it’s hand-held. Fujifilm cameras have a different system. Shutter speed and ISO are set using dials on the top of the camera. Aperture is set using an aperture ring on the lens. The Exposure Compensation Compensation dial (on my X-T1 at least) is deliberately tightened so you don’t accidentally accidentally knock it. That makes it hard to move while looking through the viewfinder. But it’s it’s easy to turn the aperture ring on the lens – and that makes it easier to use Manual moderather than Exposure Compensation to override the
EOS 5D Mark II, 85mm, 1/350 @ f2.8, ISO 800
camera’s recommended exposure settings. Everybody is different and personal preference as well as the practicalities of your camera will determine whether Exposure Compensation or Manual mode is the best way for you to take control of exposure in a given situation.
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Above: When taking photos in the shade the low contrast means that you can increase the exposure above what the camera’s meter recommend without overexposing the photo. You’ll learn more about this in the later section on exposing to the right. You can override the camera’s suggested exposure by setting Exposure Compensation Compensation to +1.0. This technique comes in useful for subjects like portraits that are often taken in the shade.
Bulb exposures The longest exposure exposure setting on your camera is 30 seconds. That will cov cover er you for many situations, but what if you need a longer shutter speed? That’s where the Bulb setting comes in. Most digital SLR and mirrorless cameras have it. You are most likely to use the Bulb setting when taking landscape photos in low light or at night, as the required shutter speed can easily exceed 30 seconds when you have a small aperture such as f16 and a low ISO dialed into the camera. You can also use Bulb to keep the shutter open while painting with light – a technique that involves using a flash or a torch to illuminate part of the subject while the shutter is open. Long exposure photography photography is a relatively new genre that has emerged with digital photography. It involves using shutter speeds of two minutes or longer to record photography. moving parts of the landscape such as water or clouds as a blur. Photographers often use neutral density filters to reduce the amount of light passing through the lens. Bulb is essential for working at these long shutter speeds. On some cameras Bulb is marked with a B on the Mode dial. On others you may find it in the shutter speed settings. Check your manual if you’ you’re re unsure.
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Left: Bulb mode is marked by a B on the mode dial of many cameras. If your camera has a separate shutter speed dial you will find it there instead. Alternatively it may be in the camera’s shutter speed menu next to the 30 second setting.
Using Bulb Bulb is easy to use. All you have to do is press the shutter button once to open the shutter, and again to close it. Use a cable release or a remote control and mount the shutter, camera on a tripod to avoid camera shake. Most cable releases have a lock so you don’t have to hold the button down yourself to keep the shutter open. You can track the elapsed time with a watch or smartphone app. Some cameras display the time on the LCD screen on the back of the body. Bulb is another form of Manual mode. Y You ou set the ISO and aperture manually, and the shutter speed by choosing how long to open the shutter for. But Bulb is different from Manual mode in that the camera gives you no indication as to whether the exposure is correct. It can’t, because it doesn’t know how long you intend to keep the shutter open for. When it comes to calculating exposure, you’re completely on your own. The easiest way to to do it is tto o start by selecting a high ISO and taking a p photo. hoto. Ch Check eck the histogram to see if any changes need to be made. Once you’ve calculate calculated d the optimum exposure at a high ISO, it’s a simple matter to calculate it at a lower setting. For example, if the optimum exposure is 5 seconds at f16 and ISO 3200, then you drop the ISO to 100 (a difference of five stops) the shutter speed needs to be extended to 160 seconds to compensate. There There is no reciprocity failure with digital cameras, and you can minimize long exposure noise by using your camera’s camera’s lowest ISO setting.
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Fujifilm X-T1, 18mm, 125 seconds @ f11, ISO 200
Above: I used Bulb to make this photo using a shutter speed of 125 seconds. This technique is called long exposure photography photography and is particularly suited to black and white. You can learn more about long exposure photography in my book The Black & White Landscape. Landscape.
Neutral density filters Neutral density filters are the secret weapon of the landscape photographer photographer.. I couldn’tt work without mine and I suspect most landscape photographers would couldn’ say the same. There are two reasons for thi this. s. The first is that neutra neutrall density filters give you control over exposure. The other is that they give you creative control over shutter speed.
What is a neutral density filter? We’ We’ve ve already learned that exposure is made up of three variables – ISO, aperture and shutter speed. In landscape photography it is normal to set a low ISO (to give high image quality) and a small aperture (say f11 or f16) for depth of field. The level of ambient light then determines the shutter speed required to obtain the optimum exposure. This is straightforward. straightforward. But we also know that shutter shutter speed is important important for creative reasons. Slow shutter speeds are good for blurring moving parts of the landscape like water or grass blowing in the wind. Sometimes, even when you set a low ISO and a small aperture, the shutter speed still isn’t slow enough to create the effect you want. That’s where neutral density That’s density filters come in. These filters are opaque opaque and block light, so that less light reaches the camera’s sensor. That allows you to use slower shutter speeds to create moody l andscape photos.
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Above: A nine stop neutral density filter from Lightcraft Workshop. The filter’s glass is nearly opaque. It only lets a small percentage of the ambient light pass through.
The strength of neutral density filte filters rs is measured in st stops. ops. That makes it e easy asy to incorporate the light blocking effect of a neutral density filter into your exposure calculations. For example, let’s say you are making a landscape photo in the evening. At an I SO of 200 and an aperture of f16, the shutter speed required to give the optimum exposure is ten seconds. You would like a longer shutter speed, so you use a three stop neutral density filter. That makes the the shutter speed required a much much longer 80 seconds. seconds. For tthis his you will need to use Bulb. If this sounds complicated complicated,, the table on this page will help you calculate the effect of using neutral density filters. Y You ou can also buy smartphone apps that help. PhotoPills is a good one (iOS and Android) and so is LE Calculator (iOS). Andr Android oid users can also try ND Calc. There’s also another co consideration. nsideration. An aperture of f16 on some some cameras ma mayy be small enough to soften the image through a process called diffraction. In the example above, the three stop neutral density filter could also be used to change the exposure settings to ISO 200, f8 and a shutter speed of 20 seconds. An aperture of f 8 gives a sharper image than f16 on some cameras. Y You’ll ou’ll certainly get less dust spots in the image at f8 than at f16, which saves time in Lightroom. As long as the depth of field at f8 is enough to make the entire scene sharp, then f8 is a good choice for the aperture.
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Shutter speed with ND filter* 9 stop 10 stop
Shutter speed without ND filter*
3 stop
1/125
1/15
4
8
1/60
1/8
8
15
1/30
1/4
15
30
1/15
1/2
30
60
1/8
1
60
2 mins
1/4
2
2 mins
4 mins
1/2
4
4 mins
8 mins
1 2
8 15
8 mins 15 mins
15 mins 30 mins
4
30
30 mins
60mins
8
60
60 mins
120 mins
15
2 mins
120 mins
240 mins
30
4 mins
240 mins
480 mins
* Shutter speeds of one minute or less are given in seconds
Neutral density filters give you flexibility in selecting aperture as well as shutter speed. If you’re using an automatic exposure mode like Aperture Priority the camera’s exposure meter will compensate for the neutral density filter, as long as the shutter speed required isn’t longer than 30 seconds. Some neutral density filters block so much light that you won’t be able to see anything through an optical viewfinder when you use them. But you may be able to see the scene in Live View or, if your camera has it, an electronic viewfinder. It’s only when the ambient light levels get really low that you won’t be able to see much in Live View or an electronic viewfinder. In that situation you need to position the camera and decide on your composition before you attach the neutral density filter to the camera’s lens.
Above: The LE Calculator app asks you to enter the strength of the neutral density filter and the base shutter speed (the shutter speed required without any neutral density filters attached). From this it calculates the required shutter speed.
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Above: The PhotoPills app has many tools of which the exposure calculator is just one. The PhotoPills calculator is more advanced and lets you change the aperture and ISO as well as select a neutral density filter.
Neutral density filter notation Even though the strength of neutral density filters is measured in stops, the naming system isn’t so clear. Manufacturers of neutral density filters use three different styles of notation. The table on this page explains the systems used. ND 0.3, 0.6 etc. The numbers tell tell you the optical optical density of the filt filter. er. An o optical ptical density of 0. 0.3 3 equals a one stop reduction in light. A two stop graduated filter has the number 0.6, a three stop filter 0.9 and so on. Simple to use if you know your three times table. ND 2, ND 4 etc. A little bit of math is required to interpret these numbers, especially the higher ones. The number refers to the amount of light that the filter allows through. An ND 2 filter lets 1/2 the light through (one stop), an ND 4 filter lets 1/4 of the light through (or 1/2 x 1/2, which equals two stops). Using these numbers you can see that a ten stop neutral density filter only lets 1/1024 of the light pass through it – less than 0.01 per cent! ND 101, 102 etc. The simplest numbering numbering system, a and nd for some rea reason son the least used. used. The last two digits tell you how many stops of light are blocked by the filter. An ND 101 filter blocks one stop, an ND 102 filter two stops and so on.
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Light reduction in stops
ND x.x
NDx
ND 10x
1
ND 0.3
ND2
ND 101
2
ND 0.6
ND4
ND 102
3
ND 0.9
ND8
ND 103
4
ND 1.2
ND16
ND 104
5
ND 1.5
ND32
ND 105
6
ND 1.8
ND64
ND 106
7
ND 2.1
ND128
ND 107
8
ND 2.4
ND256
ND 108
9
ND 2.7
ND512
ND 109
10
ND 3.0
ND1024*
ND 110
11
ND 3.3
ND2048
ND 111
12
ND 3.6
ND4096
ND 112
13
ND 3.9
ND8192
ND 113
ND 4.8 ND65536 ND 116 16 * 10 stop ND filters are usually marketed as ND 1000 filters, even though this is actually slightly less than 10 stops.
2.5 seconds
Above: I set the camera to Aperture Priority mode and made this photo without any neutral density filters and a shutter speed of 2.5 seconds at f8.
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125 seconds
Above: I added a neutral density filter and made this photo at a shutter speed of 125 seconds. I had to switch to Bulb to do so. The longer shutter speed made the sea and clouds come out much smoother.
Live View and electronic viewfinders In a digital SLR light passes through the lens and is reflected by a mirror into the pentaprism and out through the viewfinder. But what you may not know is that the mirror has a dual purpose. The camera camera’s ’s exposure sensor is also located in the pentaprism, and the camera measures the quantity of light that enters the pentaprism when calculating exposure. There are two downsides crea created ted by the location location of the exposure exposure sensor sensor.. One is that the camera can’t use the exposure sensor to measure light levels in Live View or Movie mode. The camera’s mirror lifts out of the way and no longer reflects light into the pentaprism. The other is that that light can enter enter the pentaprism from the viewfinder, viewfinder, thr throwing owing out the exposure reading and making the camera underexpose the image by as much as two stops. This isn’t a problem when you are looking through the viewfinder as your head blocks the light. But if you’re using the camera remotely and relying on an automatic exposure mode (like Aperture Priority) then you need to block off the viewfinder. Most cameras have either a built-in cover (high end models only) or a cap on the strap you can use. Alternatively you can use Manual mode to set the exposure. Most new digital SLRs have a feature called Live View, where the camera displays the view from the lens on the rear LCD screen rather than in the viewfinder.
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In Live View and Movie mode the camera gets around this by taking a reading from the sensor. It uses the same reading to display a live histogram so you can see exactly how accurate the current exposure settings are.
The electronic viewfinder view finder revolution Early digital cameras didn’t have Live View. Once the technology that makes Live View possible became widely available, the next step was to add a screen that could show a Live View feed in the viewfinder. This technology in turn made it p possible ossible to build smaller, lighter lighter cameras. This type of camera body design has become known as mirrorless and is growing in popularity. From the point of view of exposure cameras with electronic viewfinders (I’m being careful with my wording here because Sony have made several digital SLRs with electronic viewfinders) share the same benefit as you get with Live View – the ability to display a live histogram that lets you make decisions about exposure while holding the camera to your eye and viewing the scene.
Exposure simulation Some cameras have a setting that makes the Live View feed (or electronic viewfinder) lighter or darker as you increase or decrease exposure. This is called exposure simulation and is intended to give you an idea of how the photo will come out. In practice its use is limited – the only way to properly judge exposure is with the histogram. Some cameras will only display a live histogram when exposure simulation is enabled. Check your manual for details.
Above: When When a digital SLR mirror is in the down position the path of light passes through the lens, bounces up off the reflex mirror, into the pentaprism and out through the viewfinder.
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Above: In Live View and Movie mode the mirror flips up out of the way, so that the light reaches the camera’s sensor. The camera can’t measure light levels using the exposure sensor, which is located in the pentaprism. It takes a reading from the sensor instead to arrive at a suggested exposure setting.
This sequence of of images shows the Live View View feed of an EO EOS S 5D Mark II with Exposure simulation enabled. I increased the exposure for each photo by a stop (you can see the settings for each photo in the scale at the bottom of the frame). As the exposure is increased the image gets brighter and the histogram moves to the right. This photo was was taken indoors, using a light ten tentt and natural light. The contrast range of the subject is extremely low, and the histogram only covers a small part of the graph. The flower is very very light and so the camera, camera, working on the basis that the tones in the scene would average out to mid-grey, gave a suggested reading that underexposed the image by at least a stop (see second image). I used Exposure Compensation Compensatio n to increase exposure by two stops, which gave the correct exposure for this high key image (see fourth image).
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Manual lens attachments Modern lenses have electronic contacts that enable your camera to communicat communicate e with and control the aperture, autofocus and Image Stabilization functions. There are times when you may use a third party lens or other device that attaches to the camera via the lens mount but doesn’ doesn’tt have an electronic connection. Examples of such devices are: • • • • •
Plastic Holga lenses Extension tubes (basic models that have no electronic contacts) A 50mm lens reverse mounted onto the camera body for macro photography A slide copier Older manual lenses mounted onto cameras using converters.
Automatic metering works with any of these devices in Aper ture Priority, Shutter Automatic Priority and Programmed Auto modes. The best exposure modes to use with these devices are Aperture (you can set the ISO, or use Auto ISO, and the camera will set the shutter speed) or Programmed Auto (which works precisely the same way). You can use Manual mode, but you have to use trial and error to establish the correct exposure. You You can start by setting the ISO and checking the suggested shutter speed in Aperture Priority mode, then transferring those settings to Manual mode to fine-tune the exposure.
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Right: A Helios 44M 58mm f2 lens. This old Russian lens has a screw mount. I need an adapter to use it on my Fujifilm X-T1 camera. This lens was made decades before my camera. Yet my camera has no trouble measuring exposure.
I made this photos using a Helios 58mm f2 lens attached to my Fujifilm X-T1 camera using an adapter. At f2 this manual focus lens gives a swirly bokeh effect, where it looks as if the blurred parts of the background are moving around in a circle.
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Fujifilm X-T1, X-T1, 58mm, 1/200 @ f2, ISO 3200
Incident light meters No matter which metering mode you use, the accuracy is limited because the camera can only meter reflected light. This is less of a problem with digital cameras than film cameras because, as mentioned before, you can check the histogram to see how accurate the exposure is and make changes, if necessary, as you go along. But there is another way to meter the ambient light that doesn’t involve measuring reflected light. You You can use an incident light meter – you will be familiar with the concept if you’ve ever used a manual medium format or large format camera. The advantage advantage of incident light meters is that they measure the the amount of ligh lightt falling on the subject. The reflective qualities of the subject don’t matter – as long as the light levels don’t change you will get the same incident light reading from a white subject as you would from a black one. The disadvantage disadvantage is that the theyy don’t measure contr contrast ast – and won won’t ’t tell you if the brightness range of the subject exceeds what your camera’s sensor can record. Just like the figure from your camera’s meter, the reading is a suggestion and you will need to use your experience to work out if it’s the best setting to use. Incident light meters also don’t take into account filter factor. If you use a polarizing or neutral density filter you need to factor the light loss yourself. Check the filter’s instructions to confirm how to do this. The filter factor is given in stops. If the filter factor is two stops, for example, all you need to do is increase the suggested exposure that the incident light meter gives by two stops to account for the filter.
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Incident light meters also don’t account for what happens in close-up and macro photography.. As the extension (the distance between the front element of the lens photography and the camera) increases, so does the effective aperture of the lens. Your camera’s built-in meter compensates for this. Incident light meters don’t. If you don’t already own one it’s probably not worth buying an incident light meter. Your camera’s built-in meter is just as accurate. Incident light meters are only useful if you have an old film camera without a built-in exposure meter. But if you own a flash meter (for measuring the output from studio flash units) it probably has an incident light meter function as well. There’s no harm in trying it out to see if it’s useful for you. Right: A Sekonic Flashmate L-308S incident and flash light meter.
P a Rt tHRee: tHe tHRee exPosURe sCenaRIos
In the introduction I stated that exposure is simple. There is so much information about the histogram and various exposure related functions in the previous two sections that you may disagree. But this part is where it all comes together. together. I am going to show you some practical strategies for finding the optimum exposure in any situation. Exposure is easiest when your subject is static, because you have plenty of time to set the camera, take a photo, check the histogram then make adjustments if necessary. When you have the luxury of time, exposure is straightforward.
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Canon EOS 5D Mark II, 85mm, 1/180 @ f1.8, ISO 400
Things are trickier when you are faced with a fast moving situation and you have to make decisions quickly. Perhaps the ultimate example of this is a
With Raw files, on the other hand, the aim is to pack as much i nformation into the file when you take the photo as you can. You can then adjust brightness,
photojournalist in a war zone or other dangerous situation.
contrast and color balance when you process the file. In practice, as you will see, this sometimes mean that you overexpose the photo in comparison to the exposure you would choose for a JPEG file.
That’s when practice becomes important. The more time you spend using your camera, actively thinking about exposure and getting used to the controls, the quicker you can react when something happens in front of you and you need to take a photo before the moment disappears forever. The more you practice, the more the whole process becomes internalized, and you can react almost without thinking. Whatever subjects you like to photograph, and whatever types of scene you are faced with, there are three basic exposure scenarios. One of these will apply no matter what you are photographing. All three are easy to recognize, and you can select your exposure strategy accordingly. accordingly. I go through them in detail in this section. It’s important to understand that the optimum exposure may be different for JPEG files than Raw Raw files, depending depending on the situation. situation. With With a JPEG file, you are trying to get the exposure right – to record the scene more or less as you see it (or with your own interpretation, for instance if you want to make the scene darker or lighter than it really is). JPEG files can be edited in Lightroom, and you can correct errors in exposure, but this should be seen as a process of fine-tuning rather than making major adjustments. Eight bit JPEG files just don’t contain enough information to withstand major changes to contrast or brightness, and you may introduce artifacts such as banding (also c alled posterization) if you try.
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The advantage of using the optimum exposure settings is that you maximise the creative potential of your Raw files, which you can then bring out in Lightroom. But if you under or overexpose your Raw files you’ll find yourself forever fighting with them in Lightroom, trying to squeeze out detail and image quality that was never there in the first place.
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Canon EOS 5D Mark II, 85mm, 1/250 @ f1.8, ISO 800
Dynamic range is the term used to describe the range of tones that your camera’s sensor can record. The ideal situation is when the brightness range of the scene matches the dynamic range of your camera’s sensor. You know you have a photo where the brightness range and your sensor’s dynamic range match when the histogram fills the graph without going over the edges. This indicates that there are no clipped shadows or highlights. If you are using the JPEG format, your task is to make sure the histogram occupies the centre of the graph, and that there is no clipping. This is easy to verify when you come to check the histogram. If there is clipping at the shadow end, you need to increase exposure. If there are clipped highlights, you need to decrease exposure. Your aim should be the same if you use the Raw format. Place the histogram so that it’s more or less in the centre of the graph, and that neither the highlights or shadows are clipped. If the histogram falls slightly short of filling the graph, then err towards overexposure. As long as there’s no highlight clipping, selecting an exposure that overexposure. places the histogram as closely as possible to the right hand side of the graph will give the best result. Right: The histogram shows that the tones of this scene fits nicely into the dynamic range that the camera’s sensor can record. But only just – some of the shadows are clipped and it would have benefitted from an extra half stop of exposure. The light monkeys in the foreground have influenced the camera’s meter into slightly underexposing the image.
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Canon EOS 5D Mark II, EF 85mm lens, 1/180 second @ f5.6, ISO 400
Right: The histogram of this photo shows that the tonal range fits neatly matches the dynamic range of the camera’s sensor. All I had to do was select exposure settings that placed the histogram in the centre of the graph. The scene isn’t excessively light or dark, and the camera meter’s suggested settings gave a good exposure.
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Canon EOS 5D Mark II, EF 85mm lens, 1/180 second @ f4, ISO 400
S C e n A r i o T wo : The briGhTneSS r AnGe oF The SCene iS leSS ThAn The dY n A m i C r A n G e o F T h e C A m e r A’ S SenSor
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Canon EOS 5D Mark II, 85mm, 1/180 @ f2.8, ISO 6400
This happens a lot more than yyou ou might think, and and when it does it gives you a lot of freedom when it comes to exposure. You’ll recognize this type of situation when you look at the histogram and it occupies just part of the graph. All the tones are bunched together somewhere along the bottom axis. You You’re ’re most likely to see it if you shoot in overcast light, in the shade or at dusk. If you are using the JPEG format, your aim is to set an exposure that places the bunched tones somewhere in the middle of the graph. You can play around with increasing the exposure to brighten the image and move the histogram to the right, or decreasing exposure and moving the histogram to the left (be wary of this though as it may increase noise levels – you’re probably better off reducing the brightness in Lightroom). With JPEG files the aim is to get the exposure more or less as you want it to minimize any changes you need to make afterwards. Another option is to alter the camera profile to one that has more contrast, or to increase contrast in-camera. This expands the histogram and increase the photos’s contrast levels. You can do this if your subject is static and you have the time – just remember to reduce the contrast setting afterwards otherwise you may forget to reset it. However, there are times when you will want to keep the narrow contrast range of the scene because this is how it looks. A good example is a photo taken on a foggy day.
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Canon EOS Rebel XT, 24mm, 1/125 @ f3.5, ISO 100
Above: Photos taken in the shade often lack contrast. As long as you don’t underexpose the photo you can add contrast in Lightroom. The original version of the above photo (that is, without any contrast adjustments) is shown on the right.
Exposing to the right
Signal to noise ratio
If you are using the Raw format the optimum exposure changes completely in low
Any digital sensor, no matter how advanced, has noise, even at the lowest ISO
contrast situations. This This is your chance to use the expose to the right technique (often abbreviated to ETTR when you read about it online).
settings. All electrical devices suffer from noise of some sort. If you turn on a set of stereo speakers, without any sound coming through from the amplifier, you will hear a hum in the background. That’s another form of noise. You can’t hear it when you’re you’r e playing music because the volume of the noise is very low compared to the volume of the music.
Exposing to the right means that you increase the exposure so that the histogram touches, or is near, the right hand side of the graph but doesn’t cross the line. In other words, you create the brightest image possible without clipping any of the highlights. The image will probably be brighter than you would really want it, but that’s okay because you will darken it when you process the file. The aim here is not to create a file that looks the best, but to create one that contains the maximum possible information. This works with Raw files, but not with JPEG files, because of their extra bit depth. Some photographers advise that you can overexpose the image to the point where the histogram goes beyond the edge of the graph. They are working on the basis that Raw files contain more highlight details than JPEGs (the histogram is generated from a JPEG file). My recommenda recommendation tion is that you don’t do this. It may work some of the time, but sooner or later you’re going to go too f ar and clip some highlights. It’s not worth the trouble. The main benefit of exposing to the right is that it creates imag images es with less noise (especially at high ISO settings) and more detail in the shadows, without sacrificing any detail in the lightest tones.
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Photos taken with your camera’s lowest ISO settings don’t have visible noise for the same reason. At ISO 100 the amount of light that reaches the sensor during the exposure is enough to overpower any noise. There is a strong signal to noise ratio. But what happens at higher ISO settings? Let’s say you’re you’re photographing a scene in bright light and the following settings give the correct exposure: 1/125 second, f8, ISO 100 But later on in the day, as the light fades, you need to raise the ISO to 1600 to take a correctly exposed photo with the same aperture and shutter speed. The light level has dropped by four stops, and only 1/16th of the light will reach the sensor during the exposure. The camera compensates compensates for this by amplifying the data collected by the sensor. At the same time, it also amplifies the noise levels, and that’s why noise levels increase along with ISO. The higher the I SO you use, the less light reaches the sensor during the exposure, and the lower the signal to noise ratio.
By exposing to the right, you are increasing the exposure, and more light reaches the sensor when you take the photo. The signal to noise ratio is greater and the result is an image with less noise. The darkest tones tones in the photo have also received received more light which means that they have more detail and greater tonal separation. The advantages advantages gained by expo exposing sing to the right makes a powerful argument for using the Raw format, which is why so many photographers do so. There is one disadvantage disadvantage to exposing to the the right. Increasing the exposure means that you need to use a slower shutter speed or a wider aperture. This is okay if those settings work from a creative point of view, or if the camera is on a tripod. But may cause an issue if you are hand holding the camera and need a certain shutter speed to avoid camera shake,
These examples show how exposing to the right works in practice. In the first image, taken at the camera’s recommended exposure settings, the histogram shows that the subject doesn’t have a great deal of contrast. It doesn’t cover the full range of the
but no highlights have been clipped. This image, once processed, will have less noise than the previous one.
or a certain aperture for sufficient depth of field. You can always raise the ISO, but this will negate some of the benefits obtained by exposing to the right. If exposing to the right isn’t practical for any of these reasons, don’t feel that you have to do it. It’s just another technique at your disposal to use when the time is right.
graph – the right hand fifth is empty, and that tells us that we can increase exposure by a stop without clipping any highlights.
by two stops. The histogram is cut off on the right-hand side, indicating that there are clipped highlights. The Highlight Alert confirms this. While it may be possible to pull the lost detail back in post-processing, it’s far better to make sure the image isn’t overexposed overex posed to start with.
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The next image shows what happened when I increased exposure by a stop. The histogram is further to the right,
The final image shows what can happen if you increase exposure by too much. Here, I’ve increased the exposure
These samples show show the relationsh relationship ip between exposure exposure and noise. Each one is taken from the centre of a photo taken with an EOS 5D Mark II. Two were taken at ISO 1600. I took one using the expose to the right method, and deliberately underexposed the other by a stop then brightened it in Lightroom to compensate. When you compare the results, the underexposed image has much more noise and less fine detail than the correctly exposed one. ISO 1600 (underexposed) (underexposed) I took another photo of the same flower at ISO 6400, also using the expose to the right technique. It has more noise than the correctly exposed photo taken at ISO 1600. This is to be expected – the additional noise is caused by the higher ISO setting. But the noise levels are also much less than in the underexposed photo taken at ISO 1600. The comparison proves that exposure is just as important as ISO when it comes to minimizing noise levels. It also demonstrates that if you are faced with a choice between underexposing an image, or using a higher ISO to obtain the correct exposure, you will obtain better results by raising the ISO.
ISO 1600 (exposed to the right)
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ISO 6400 (exposed to the right)
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Fujifilm X T1, T1, 14mm, 1/125 @ f8, ISO 200
Sometimes you will encounter a scene with a brightness range greater than what your camera’s sensor is capable of recording. This is most likely to happen in bright sunlight or if you are photographing a landscape where the sky is much brighter than the foreground. foreground. In this case the histogram may expand all the way across and beyond the available space in the graph. You are faced with a choice of clipping either highlight detail or shadow detail. Whenever you encounter a situation like this it’s important to understand that all that’s happened is that you’ve bumped up against the limits of what your camera’s sensor can do. That’s okay – there are limits wherever you look in photography, and good photographers learn to work and create images within the capabilities of their equipment. Adopting this approach avoids some of the frustration involved in trying to push your equipment beyond its limits. One of the first things you need to look at is the nature of any clipped highlights. Are they specular highlights? In which case they may be no big deal and you can continue. The other thing to consider is tthe he lighting. Does the the lighting suit tthe he subject? If the contrast is too high for your camera’s sensor to cope with, that suggests you’re shooting in bright light, or that there are a lot of light tones and dark tones in the image. It may be that all you need to do is change the light source. For example, if you take a portrait of a woman lit by direct sunlight you are going to create lots of problems, and not just with exposure. Your model will squint in
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Canon EOS 5D Mark II, 85mm, 1/250 @ f4.5, ISO 800
Above: There are specular highlights on this vintage car’s hood ornament. The presence of clipped highlights on metalwork does not indicate a problem with exposure. They are a natural part of this type of photo. You can only control specular highlights if you have control over the li ghting, and you need a studio for that.
the bright light. There may be shadows across her face. The hard light won’t be flattering to her skin. The easiest solution solution is to tut your model in the the shade. The light is softer an and d more flattering. The brightness range of your subject should fall into the range your camera’s sensor is capable of recording, solving most of your exposure related problems in one go. The same applies to landscape ph photography otography.. Are you shoo shooting ting in direct sunligh sunlight? t? Why not come back in the early morning or late evening when the sun is low in the sky, close to the horizon? The contrast is going to be reduced and the light will be better. You’ll create a stronger image and solve your contrast problem at the same time. Admittedly, Admittedly, with landscapes the difference in brightness between the sky and the foreground may be too much even in relatively soft light. In that case, there are some strategies to cope. Another consideration is how important is the shadow detail? Yo You u can create strong images in hard light by exposing for the highlights and letting the shadows go dark. There’s There’s no rule that says you have to capture all the detail in the scene. Dark shadows tend to look okay – highlights don’t, but the problem is an aesthetic one. If there was an aesthetically pleasing way to blow out the highlights then that would be okay. It’s just that the best way to do it is to use film, not a digital camera.
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Fujifilm X-T1, 18mm, 1/125 @ f3.2, ISO 6400
Above: The Muslim Quarter in Xi’an, China. It was nearly dark when I made this photo, and I had to set the ISO to 6400 to capture it. The sky is much brighter than the building. I didn’t want to overexpose it and lose the cool blue color. But I couldn’t get detail in both the sky and the buildings. That was fine with me as I wanted to capture the glow of the lamps against the walls. This is what gives the photo mood and emotion. The hidden detail isn’t required to achieve this.
Changing viewpoint Another thing to look at is the background. Is it brighter or darker than your subject, so much so that you would lose highlight or shadow detail if you exposed for the subject correctly? Can you change your viewpoint or move your subject so that you don’t have such a difference in brightness between your subject and the background? Will Will the situation change if you come back at a different time of day, when the sun is shining on the scene from a different angle? What What if you come back on a cloudy day – will the soft light suit the subject better? It may be the best solution is for you to return when the lighting conditions are different. This This is not just a practical consideration, it’s an aesthetic and creative one too. Another solution may be to change the focal length of the lens you are using. Wide-angle lenses take in more of the subject, and this may include too bright a contrast range for the camera to render properly, properly, especially if part of the scene is in shade and part of it in the sun. Getting closer, or changing focal length so that less background is included, may change that. Canon EOS 40D, 32mm, 1/160 @ f7.1, ISO 200
Above: This cathedral in Argentina looked beautiful, lit by the light of the setting sun. But the strong backlighting meant the sky was burned out. So I waited until the sun was as low in the sky as possible, and moved so that it was hidden behind the statue on the right. The bottom right of the photo is still overexposed, but I minimized the effect by changing my viewpoint, and the result looks natural.
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Canon EOS Rebel XT , 18mm, 1/125 @ f8, ISO 100
Above: If the brightness range of scene means that your camera’s sensor can’t capture all the tones then is there a way to use this creatively? A fairly obvious example is a silhouette, such as the one in the image above. I couldn’t capture all the detail in the cactus and the statue as well as the sky in a single exposure. So I used the dramatic sky to create a silhouette.
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Canon EOS Rebel XT , 18mm, 1/60 @ f8, ISO 200
Above: A shaft of sunlight ill uminated the clothes hanging in this rural store in north-west Argentina. The brightness range of the scene greatly exceeded what my camera was capable of recording. So I searched for a composition that utilized the contrast between the clothes and the dark background. This creative to approach relies on your observational skills and understanding of light and composition. It’s about using the light, not fighting it.
Use a diffuser The photo on on the near right sho shows ws what can happen happen when you try and take a photo of a flower in direct sunlight. The harshness of the light creates two problems. The first is aesthetic. The light is ugly. You can’t create a beautiful image of a flower in these conditions. The second is to do with exposure. The difference between the brightest areas, lit by the sun, and the areas in shadow is too much for the camera’s sensor to cope with. The solution was was to place a d diffuser iffuser between the the sun and the flower. Diffusers look like reflectors but are made of transparent rather than reflective material. They reduce contrast contrast by soften softening ing and spreading out the light. In this case, even with the diffuser, diffuser, the light was still too hard. I replaced the diffuser in its black cover and asked my wife to hold it over the flower so that the shadow covered the fuchsia and (just as importantly) the greenery in the background. The even light made it easy to take a photo without any problems caused by high contrast (far right). Diffusers are available in large sizes for taking photos of people in direct sunlight. Canon EOS 5D Mark II , 85mm, 1/250 @ f2.5, ISO 200 (diffused photo)
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Portable flash and reflectors The use of portable flash and reflectors a applies pplies mostly to portrait photography. If the background is brighter than your sitter, you can use a reflector to bounce light back onto them, or a portable flash to light them. You can even light them so that they are brighter than the background. This opens up a whole series of creative options. There is so much to flash photography photography that it ’s beyond the scope of this book to go into detail. Here’s an example using a reflector. We were shooting late in the afternoon but the light was still very hard. As you can see in the photo near right, half of my model is in deep shadow. It’s not a flattering look, and I can’t lighten the dark areas much in postprocessing as the camera hasn’t captured much detail there. The solution was was to ask someo someone ne to hold a reflector reflector to bounce bounce the sunlight back onto her right side. This evened up the lighting and made it much easier to create a strong image (far right). In bright sunlight like this it’s best to use a white reflector – the strength of the glare from a silver reflector may harm your model’s eyes. This photo was was taken on the sa same me afternoon as the the one on page 12. It’s much better than the backlit image and shows the benefit of trying to work with the lighting conditions, and the principles of good exposure, rather than against them.
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Canon EOS 5D Mark II , 85mm, 1/180 @ f4.5, ISO 100 (both photos)
High contrast in the landscape Landscape photography photography is a little different from other subjects because you often want to include the sky, and the sky is naturally brighter than the foreground. Sometimes you can use this to your advantage, and let the foreground go dark. The ultimate example of this is a silhouette. But what if you want to capture detail in the foreground as well as the sky? One option is to lighten the foreground in Lightroom. But if the foreground didn’ didn’tt receive much light during the initial exposure there’s a limit to how much detail you can bring out. Right: One way to solve the problem of a high contrast scene is to wait until the sun has set. For the next 20 minutes or so the light from the sun comes from below the horizon and bounces off the clouds, creating a beautiful, reddish-pink light that illuminates the landscape with a soft glow. The brightness range of the scene is much less. This works best with seascapes as the light is also reflected from the sea.
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Canon EOS 5D Mark II , 29mm, 120 seconds @ f16, ISO 50
Graduated neutral density filters Another solution is to use a graduated neutral density filter. These have been essential equipment for landscape photographers for decades. A graduated neutral density filter is like a neutral density filter except that one half is clear, and the other is dark. The filters are square or rectangular in shape and attach to the front of your lens using a purpose made holder that allows you to move the filter up or down to align the centre, where the dark and clear halves meet, with the horizon. Graduated neutral density filters are a useful tool but they do have drawbacks. Good quality filters are not cheap, and you may need a set of filters of different strengths to deal with different lighting situations. Above: These diagrams Another drawback is that graduated neutral density filters work best when the horizon is a straight or nearly straight line. If the horizon is an irregular shape, the filter may cut through the wrong part of the landscape.
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show what neutral density graduated filters look like. The transition between opaque and clear can be either soft (top) or hard (bottom).
Fujifilm X-T1, X-T1, 18mm, 340 seconds @ f8, ISO 200
Above: I needed a three stop neutral density filter to create this landscape photo. In the original image (right) the brightness of the sky meant that I couldn’t capture detail in both sky and foreground without assistance.
Exposure blending Exposure blending is a simple technique where you take two photos at two different exposure settings. One is exposed for the sky, and the other for the foreground. You then combine the two correctly exposed parts of the image in post-processing (you’ll need a program like Photoshop for this as you can’t do it in Lightroom). The camera should be firmly mounted on a tripod so that the two images align. The advantages advantages of exposure blen blending ding are that yyou ou don’ don’tt need to buy neutral density filters, and the technique works with irregular horizons.
HDR Another technique you’ll come across that is popular is High Dynamic Range (HDR) photography. photography. This is where you take two or more images of the same scene with bracketed exposures and use a program that processes them into a 32 bit image and then converts that, using a process called tone mapping, into an eight or 16 bit image that you can then view on a monitor or process further in Lightroom or Photoshop. Lightroom is very good for this as it creates natural looking HDR images, avoiding the overcooked look possible in many plugins. It is easier to create a HDR image in Lightroom than it is to exposure blend in Photoshop.
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Fujifilm X-T1, 18mm, f11, ISO 200
One stop underexposed
Above: I created this image with the merge to HDR tool in Lightroom. I merged two photos, one underexposed by a stop to capture the detail in the sky, the other overexposed by two stops to capture foreground detail. The original photos are shown on the right. Two stops overexposed
+
=
Exposure blending and HDR are not just for landscapes. If you are taking a photo
The second image image shows what h happened appened when I ex exposed posed for the w window. indow. The
indoors and include a window in the image there will be a big difference in brightness between whatever you are photographing inside and the light coming through the window.
details in the stained glass has been recorded nicely, but the foreground is very dark. It hasn’t worked.
These photos show what happ happens ens when you try to capture this type of scene with a single exposure, and without any supplementary light (such as portable flash) to light the foreground. One option is to expose for the foreground, and let the window light burn out (left).
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I created the third image by blending the correctly exposed parts of the first two images in Photoshop. Even though the camera was hand-held the images were aligned closely enough for this to work. The result – a photo that shows detail in the all the important areas.
PaRt foUR: ex PosUR e anD CReatIvIty
As we learned near the start of the book, there are usually several different aperture, shutter shutter speed and ISO combinations you can use to obtain the optimum exposure. The considerations to take into account when deciding which settings to use are both practical and creative. For example, is the shutter speed fast enough to prevent camera shake, or slow enough to capture motion blur? Is the aperture small enough to give sufficient depth of field or wide enough to create beautiful bokeh? The final section of this book looks at some of my favorite images and the practical and creative exposure related decisions behind them.
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Fujifilm X T1, 35mm, 1/180 @ f3.6, ISO 3200
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Canon EOS Rebel XT, 38mm, 1/125 @ f10, ISO 200
Old car, La Plata, Argentina Old cars are always photogenic and this vehicle that I came across while wandering around the city of La Plata in Argentina is no exception. I was drawn not just to the old car itself, but the way the light from the setting sun crept through the window and illuminated the car seats. The interplay between light and shadow is key to the success of the composition. The warm sunlight created mood, but so did the shadows. Lack of shadow detail helps create a sense of mystery. Exposure was a simple matter of making sure the highlights didn’t burn out and that there was no camera shake. The highlights are the most important part of the photo and I needed to preserve them. I achieved it by using Evaluative metering metering in Shutter Priority mode with Exposure Compensation set to -1/3 stop. Exposure: 1/125 second @f10, ISO 200 On the right is another photo where the shadows are an important part of the composition. It’s a study of light, shadow, form and shape. Modern camera sensors are very capable. Raw files often contain a lot of shadow detail. You can reveal it using the Shadows slider in Lightroom’s Develop module. But how much detail you reveal is up to you. You may even want to make the shadows darker and create deep black areas in your photos. Exposure and the creative decisions you make in postprocessing work together to create the final photo.
Fujifilm X-T1, 35mm, 1/250 @ f16, ISO 200 96 | Mastering Exposure
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Canon EOS 5D Mark II, 24mm, 8 seconds @ f11, ISO 400
Playing with fire, Wellington, New Zealand A friend of mine has a hula hoop with wicks around the outside. She sets the wicks alight and then spins the hoop around her body. Do this outside, at night, in an appropriate setting and you can create photos like the one on the previous page. The scene was lit by the light produced produced by the flames of the hoo hoop, p, so light le levels vels were low. I set my camera on a tripod to avoid camera shake. I needed a shutter speed long enough to capture the motion of the flames. I used Manual mode rather than Aperture or Shutter Priority as I wanted the exposure to be consistent from frame to frame. Exposure: 8 seconds @f11, ISO 400 Canon EOS 5D Mark II, 24mm, 8 seconds @ f8, ISO 400
Exposure in situations like these involve a certain amount of trial and error. Y You’ll ou’ll need a low ISO for good image quality and an aperture small enough to give good depth of field. It takes experimentation to find the best shutter speed. If it’s too short it will cut off the flame trails. Too long, and the flames will merge into other, spoiling the pattern. Try not to overexpose overexpose the the flame trails, b but ut expect some clipped highlights highlights.. There are two more photo photoss from the shoot on the right. The exposure ffor or both is exactly the same. Note: Fire is dangerous. You You should only try this with a trained professional fire performer.
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Canon EOS 5D Mark II, 24mm, 8 seconds @ f8, ISO 400
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Fujifilm X Pro 1, 18mm, 4 seconds @ f11, ISO 1600
The FutureHoop, Wellington, New Zealand Another friend of mine has a FutureHoop – an electronic hoop with built-in lights that you can program to flash in different sequences and patterns. pattern s. We We made the photos at a local memorial which provided a dramatic backdrop and gave her the space she needed to move with her hoop. I worked in Manual mode and tried several shutter speeds to find the best settings to record the shapes and patterns created by the movement of the FutureHoop. Exposure: 4 seconds @ f11, ISO 1600 We arrived on location just after sunset. The fading light created another challenge. The first images from from the shoot w were ere taken at 2 seconds @ f11, ISO 200. The final ones need an exposure of 4 seconds @ f11, I SO 1600 – a difference of four stops. I managed exposure by working in Manual mode and looking at the histogram after each set of photos. As the light faded, the histogram moved to the left. As this happened I extended the shutter speed or increased the ISO to compensate. As a result the earlier photos had brighter backgrounds because of the higher levels of ambient light. When I developed the images in Lightroom I darkened the backgrounds in the earlier images so that the background looked more or less the same. This is another example of how post-processing and exposure work together to create the final image. There are two more photo photoss from the shoot on the right.
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Fujifilm X-Pro 1, 18mm, 4 seconds @ f11, ISO 1600
Fujifilm X-Pro 1, 18mm, 4 seconds @ f11, ISO 1600
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Fujifilm X T1, 56mm, 1/550 @ f2.8, ISO 6400
Long Shen Dao, Auckland, New Zealand Long Shen Dao are a Chinese reggae group. They were playing at the Auckland Lantern Festival. They They were very good – I didn’t didn’t even know that Chinese reggae was a thing before I saw them. The light levels were were continually ch changing anging as the stage lights moved around and turned on and off. I set the camera to Aperture Priority, opened up to f2.8 and set the ISO to 6400. This gave me fast shutter speeds for freezing movement. It also provided plenty of margin for error. The shutter speeds were still fast enough to prevent camera shake even when the light dropped. The camera tended tended to overexpose, overexpose, ev even en with Evaluative Evaluative metering metering.. I had to set Exposure Compensation to -1 1/3 stop to compensate. This took a little trial and error and careful analysis of the histogram. I needed to ignore clipped highlights created by the spotlight and concentrate on the guitarist’s face – the most important tone in the photo. But once I’d figured out the required settings I was free to take photos and concentrate on composition and capturing the best moments, knowing that the exposure was taking care of itself. Exposure: 1/550 second @ f2.8, ISO 6400 There’s another phot photo o from the concert concert on the right.
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Fujifilm X T1, 56mm, 1/280 @ f2.8, ISO 6400
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Fujifilm X T1, 35mm, 180 seconds @ f5.6, ISO 200
Liencres, Cantabria, Spain These spectacular rock rock formations near near the Spanish city of of Santander are perfect for long exposure photography. I used a ten stop neutral density filter to obtain the 180 second exposure I used for the photo. The first step was was to take a photo photo and calculate calculate the optimum optimum exposure b before efore adding the filter. This gave me an exposure of 1/15 second @ f8, ISO 200 (you can see the photo on the right). I used a graduated neutral density filter to make the sky darker. I added a ten stop neutral density filter, which gave me a shutter speed of around 34 seconds at f5.6, and used Bulb to open and close the shutter. But strange things were happening with the histogram. It was a warm, humid and cloudy day. The light was so even that the histogram was very narrow. That meant I could increase the exposure all the way to 180 seconds without clipping any highlights. The three minute minute exposure blurred blurred the water water beautifully, giving me the look look I wanted. I added contrast back into the photo in Lightroom. Exposure: 180 seconds @ f8, ISO 200
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Fujifilm X-T1, X-T1, 35mm, 180 seconds @ f5.6, ISO 200
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Fujifilm X T1, 18mm, 20 seconds @ f2.8, ISO 6400
Tekapo, New Zealand The Church of the the Good Shephard Shephard in Tekapo Tekapo on New Zealand’s Zealand’s South Island is one one of the country’s iconic viewpoints. The church is located in a dark sky reserve. The lack of artificial light makes it ideal for observing and photographing the stars. There’s a large telescop telescope e on a nearby mo mountain. untain. The The aqua blue w waters aters of Lake Tekapo are are just behind the church. The church is such a well known attra attraction ction that peop people le kept coming d during uring the evening to see it. Tourists came in buses and walked around the church, taking photos with their mobile phones, oblivious to the photographers working with cameras on tripods. All quite amusing, and I decided to make some photos that included the blurred figures. Astrophotography is usually done with a wide-angle lens to capture the breadth Astrophotography of the sky. You need a high ISO and a shutter speed of around 20 seconds to capture the stars in the sky. If you drop the ISO and use a longer shutter speed the movement of the earth will turn the stars from pinpoints of light into star trails – another type of photo entirely. Exposure: 20 seconds @ f2.8, ISO 6400
Fujifilm X-Pro 1, 18mm, 20 seconds @ f2.8, ISO 6400
An easy way to calculate the optimum shutter speed for star photography is to use the formula 500 / 35mm equivalent focal length = shutter speed. In this case, as I used an 18mm lens on an APS-C camera, the formula is 500 / 27 = 18.5.
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Above: Later on, I was also able to capture the Milky Way as it rose above the church.
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Canon EOS 5D Mark II, 85mm, 1/350 @ f2.8, ISO 400
Wimmy, Wellington, New Zealand It’s always important to calculate the optimum exposure required. But you’ll really notice the effect if you get it wrong with a portrait. Underexposing skin emphasizes wrinkles and other sk in blemishes that people normally prefer to hide. Overexpose and you’ll get clipped highlights in the skin and the whites of the eyes. I used a short telephoto lens (85mm on a full-frame camera) to create the portrait on the previous page. I set aperture to f2.8 to blur the background. I tend to avoid f1.8, the widest aperture on this prime lens, because the depth of field is too shallow. F2.8 is a nice sweet spot that gives good bokeh without blurring the model’s face too much. I prefer to work in Manual mode for portraits. Once you’ve calculated the optimum exposure you can leave those settings locked in and concentrate on directing your model. Using Manual mode lets you get on with this, rather than worrying about exposure. This works as long as the light doesn’t doesn’t change. If it does, you sh should ould check your exposure settings to make sure they are still optimal. Exposure: 1/350 second @ f2.8, ISO 400 There’s another portrait fr from om our shoot on the right.
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Canon EOS 5D Mark II, 85mm, 1/500 @ f1.8, ISO 200
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Fujifilm X T1, 56mm, 1/250 @ f2.8, ISO 6400
Todd the Flute Maker, New Zealand I learned of Todd and his work making flutes while working a personal project to photograph craftsmen at work. On this day he showed me how he made a wooden flute in his garage workshop. It was an overcast day. We worked with the light that came through the open garage door. He had artificial lights in the garage, but I asked him to turn them off. Mixed lighting creates problems with White Balance in color photos. It’s not a problem for black and white, but as I intended to process photos in color as well it was best to turn them off. Light levels were low and I had to work at ISO 6400. I exposed to the right, and as a result there’s very little noise in the photo. T This his shows just how capable modern digital cameras are at high ISO settings. I set the aperture to f2.8, mainly because of the low light. I avoided wider aperture settings as I didn’t want the depth of field to be too shallow. For the photo on the previous page Todd put the flute on a lathe and used a tool to shape it as it spun around. I wanted to use a shutter speed fast enough to prevent camera shake, and slow enough to record the blur of the spinning flute. A shutter speed of 1/250 second did the job perfectly. Exposure: 1/250 second @ f2.8, ISO 6400 There’s another phot photo o from our shoot shoot on the right, also taken at ISO 6400 and 1/250 second. The moving machinery is blurred in this photo too.
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Fujifilm X-T1, 56mm, 1/250 @ f2, ISO 6400
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Fujifilm X T1, 56mm, 1/1100 @ f1.2, ISO 1600
The Balkanistas performing in Wellington, Wellington, New Zealand I went to see local band The Balkanistas perform in an open air arena. I took some photos, like the one on the right. It’s not bad, but it doesn’t capture the energy and excitement of the evening. How do you capture energy in a photo? Often the answer is to include some kind of movement. Movement, or blur, implies motion. Motion requires energy. So I started experimenting with slow shutter speeds. I set the ISO to 200 (the lowest it goes on my Fujfilm X-T X-T1) 1) and the aperture to f16. I set the camera to Aperture Priority and let it calculate the exposure. The lights were changing color and brightness so I couldn’t use Manual mode. I found that I needed to set Exposure Compensation to -2/3 stop to prevent overexposure. Once I had worked all this out I was free to experiment. I took photo after photo, moving the camera around in different directions during the slow exposures, which varied from 1 second to 4 seconds in length. The result was a series of abstract images that portrayed something of the energy and excitement excitement of the event. Exposure: 2 seconds @ f16, ISO 200 Above: This photo, taken at 1/1100 second, shows a more literal version of the band performing in front of the crowd at the open air arena.
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ConClUsIon
The subject of exposure is often over-complicated, but it doesn’t have to be that way. Just remember that for the best results you should use the Raw format, avoid clipping highlights and expose to the right when you can. It really is as simple as that. Let your camera’s sensor take care of the rest. As the technology advances, and dynamic range improves, you’ll find that your Raw files become better and so does the technical quality of your photos. As always, if you have any questions about the content of this book then please send me an email at
[email protected].
Happy shooting, Andrew S. Gibson www.creative-photographer.com
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Fujifilm X T1, 35mm, 1/180 @ f5.6, ISO 3200
Beautiful ebooks for photography photograph y lov lovers.. ers.. .
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