The Bronica Focus Problem

September 7, 2017 | Author: ruifeijao | Category: Camera, Lens (Optics), Aperture, Optical Devices, Natural Philosophy
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THE BRONICA FOCUS PROBLEM AND HOW TO SOLVE IT by Sam Sherman ([email protected]) 5/26/99

The Bronica S-2, C and S-2A, as similar cameras, share a focusing problem. The frame holding the ground glass down in proper position has foam which deteriorates with age and allows the screen to move up out of alignment. You will not see a sharp image in the finder at the infinity setting on the normal f2.8 75MM Nikkor lens - wide open. That is the clue this problem has taken place. My advice on how to solve the problem: 1- If you are not handy - print out this page - take the camera to a good repairman. 2- If you wish to do the repair yourself - Be careful- you risk breaking the ground glass or worse. This said, we continue. 3- Remove the Waist Level finder. 4- You will note a black painted metal frame holding down the ground glass. There are 2 screws to remove at the Northern position on the frame. Remove these two screws only. 5- Slowly slide the frame forward - it slips under the two screws at the rear or lower or Southern position. It may have the ground glass adhering to it due to a sticky substance on the frame. Remove the ground glass from the frame. Scrape the deteriorated foam from the bottom of the frame. I use an X-Acto knife with a flate blade - a single edge razor blade will do. Then clean the residue on the frame with a solvent. 6- Clean the ground glass with a solvent too. Then finish with light soap and water and dry carefully with cloth or tissue. 7- Be careful of the plastic fresnel screen below the groundglass. Notice its position and which side goes down. Clean only with slight air from an ear syringe. Replace in camera. 8- I suggest using Moleskin to replace the foam. This is adhesive backed felt used for foot problems. Buy a medium sized roll in your local Pharmacy for about $5.00. I cut thin strips of it a little less than 1/4 inch wide. At the North and South positions of the underside of the metal frame - use a single layer. On the sides (the East and West positions - use a double layer). 9- Clean ground glass with ear syringe and replace over fresnel screen in camera. The screen should move down to a point where it rests properly on the upper and lower

metal bar supports. 10- Then slide in the metal frame into the screws at the back (South) position on camera body. If the groundglass and fresnel screen are seated properly you should be able to press down the metal frame and - replace the two screws that hold it down. BE CAREFUL HERE - This is the step where sloppy handling can crack the ground glass. And replace the Waist Level finder. Using the Waist Level Finder with critical magnifier in place - check your camera with the 75MM lens wide open - Focus on an infinity target - a distant house or Tree or Street Light- as you focus your camera the image should snap into Sharp Focus. The camera will now focus properly at all distances. ------------------------------------------------------------------------------- -----The Bronica focusing problem was the fear that Nikon had when they first made their lenses available to Bronica: somehow the camera would not focus sharply and their great lenses would get a bad reputation. I have heard of people selling their Bronica S-2, C and S-2A cameras because they could not get critically sharp photographs. Here is the problem and its solution. These restored Bronica cameras, in combination with good Nikkor optics, are capable of delivering sharp photos that will equal or exceed the quality of images from any Medium Format Camera - Old or New! - Sam Sherman

BRONICA FOCUS PROBLEM - SOLUTIONS- part 2 I have just gone to replace the finder foam in my Bronica S-2 and was I surprised. While I expected this camera to be a later model than my "C", it turns out to have the earlier screw clamps to hold the screen down like Bronica "S" and "Deluxe". Even though it has the deteriorated foam, the screw clamps prevent the groundglass from moving up and out of focus. I decided to clean off the old foam anyway and found that unlike the Bronica "C" and "S-2A" there were two more screws at the South end of the frame which had to be removed on this model to remove the frame. Between the groundglass and the fresnel screen were three framing shims set by the factory to set the finder to infinity focus. In the "S-2A" there was one thin shim under the bars which the groundglass rests on at the North and South of the finder wel l. Whether these shims help you to get exact infinity focus or place the groundglass somewhere else is another story. I have never trusted things like this and have made my own tests and removed some in the past - we will see what my new Bronica tests pro ve. On another related subject - most 120 film bows into the 6x6 aperture in an irregular manner from photo one to photo 12. In some cameras I have found the film puffier in the first few shots and lying flat in the last few. If you shoot at f8 and smaller openings

depth of field will cover up some of these problems. This is not as prevalent to this degree in 35MM cameras and that is why you can shoot at F2, f1.4 etc. Users of Medium Format must know their cameras and the format to get maximum results. - Sam Sherman

BRONICA FOCUS PROBLEM - Part 3 - Addendum In focusing sharply using Bronica focal plane shutter cameras and others, it is important that when the lens is set at the infinity point on the focusing mount - that the lens is at the Point of Sharpest Focus at the film plane in the camera. This assumes that the focusing mount is completely accurate and when it stops at the infinity point, the lens is focused precisely at infinity, not slightly off that point. Second to this is the fact that the Viewfinder Ground Glass at that infinity point shows the image in the finder as the Point of Sharpest Focus. Some finders may seem to show a sharp image, but as they can be slightly out of alignment, they do not show the Point of Sharpest Infinity Focus, when the lens is doing so on the film. Adding to this is the difference in focusing screens in classic Bronica cameras. The earliest models - Z, Deluxe, S and early models of C and S-2 have the early focusing screen/ground glass combination. This combination is noted by the four screw clips that hold the ground glass down in its four corners. This early screen shows a "crisper" image in the finder at the Point of Sharpest Focus than the later S-2A screens. That does not mean that an S2-A screen does not show a sharp image, or that the user cannot delineate the Point of Sharpest Focus. It only means that the early screens, with a sharp contrasty lens, can show a finder image that is crisp, contrasty and almost 3-D looking. This has nothing to do with how sharp the image is on film. Early cameras all used ground glass alone as their finder screens or in the back of sheet film cameras. Not all ground glass is equal in showing a sharp image. But in general, ground glass screens by themselves will show a sharper image than plastic screens and ground glass/plastic fresnel lens combinations. Early Exakta 35MM cameras, Pentacon 6, some Zeiss Ikoflex TLRs and others have used a glass condensor lens which is ground glass on the lower side for the finder. This was brighter than the ground glass alone, sharper than fresnel combinations and not as bright as today's plastic fresnel screens. Modern finder screens need their focusing aids to work best - split image, microprism etc. This is due to diffusion of the image that plastic causes. The ground glass area is not as certain in establishing the Point of Sharpest Focus as an old plain ground glass

screen. Ground glass/fresnel combinations as used in old Bronicas have additional problems in alignment caused by the fresnel screen diffusing the image and refraction of the image caused by the fresnel screen. In conclusion - I have previously stated that old Bronica C, S-2 and S-2A cameras (and possibly others) MUST have the deteriorating foam on the frame holding the ground glass down replaced to assure the user of getting sharp finder images matching what the film is seeing. Now, what of the buyer of a new "used" camera, what is he getting? Ideally there should be a small "m" tag put on all modified Bronicas, like the labels put on the back of modified computers. But, who would do this uniformly? Instead, many upgraders have replaced the black foam with a light colored felt or something similar. To note this, remove the lens focusing mount from the camera and look inside it up at the fresnel/ground glass screens and you may see a light colored material framing the screen all around it. If one sees this it is a pretty good bet that this modification has been done. In all other cases, it is wise to have this checked and if not done, modified at once if you are actually using the camera, not only collecting it. Good luck! - Sam Sherman

[Ed. note: see related article on film flatness] Date: Mon, 20 Sep 1999 From: "S. Sherman" [email protected] To: [email protected] Subject: [BRONICA] Fine Tuning Focus on Focal Plane Bronicas This is the update on the above article: When I had a focusing problem on my Bronica C, I explored replacing the finder foam, which I have now done successfully on three cameras and which led to my writing the above article. However, that is not the end of the story. Once I replaced the finder foam, I still could not get a critically sharp (crisp) image in my finder with the lens set to infinity. Something was still wrong after replacing the foam. I realized this when I took my helical focusing mount and lens off the camera and held the lens by itself in front of the mirror - careful not to scratch it. I could focus to infinity and past it -getting a crisper image at infinity than I could get with the focusing mount set to infinity. This proved to me that the finder ground glass was still positioned past infinity even with the defective foam replaced. To check this out, I made a focus viewer by taking an old 6x6 ground glass from a junker TLR and epoxying a loupe to the shiny side. Once I lock the shutter release open at "B" I can replace my back without insert, put the ground glass and viewer right on the film aperture track and view exactly what the film is seeing on a sharp, contrasty infinity target. I have used 75MM f2.8 Nikkor wide open at f2.8 and the 100MM

Zenzanon at f2.8 is even better. On the 3 above-listed cameras, viewing on my ground glass unit, with lens set to infinity, the image was "crisp", while it was a little muddy in the finder, even with the foam replaced. In short, the finder ground glass was still too high up and past the infinity setting. On my S-2 I found metal shims under the ground glass, removed them and then could get a "Crisp" finder image. Also testing this at a 4 foot away target worked fine. Several rolls of film shot with a tripod were all very sharp. On my "C", with no shims inside, only removing the two metal ledges at the north and south positions could result in moving the ground glass down enough to be at exact infinity with "crisp" finder images. Two rolls of film, shot with lenses wide open yielded sharp images - using a tripod. (Due to the 2 removed metal ledges - I had to add more moleskin/felt to the frame to hold the ground glass down at a lower position.) Same problem on the S-2A still to be treated. I cannot find a screw setting to adjust infinity focus on these cameras as it is not obvious on them, not in the SPT/ Bronica Repair Notes and would have to be something that changes the position of the mirror at rest position. There could be such an adjustment, but it may require time consuming disassembly of the camera side plates, which is a big time waste to set infinity adjustment. Cameras, including Pentacon 6, Kiev 60 and Primarflex, have 4 screws easily accessed to adjust the ground glass height to get exact infinity focus. If Bronica has no such adjustment, the factory made the camera to close precision tolerances and then used thin metal shims of varying thickness to get the groundglass into infinity sharp focus. Either something changed the mirror position over the years (one of my cameras is new and unused - so heavy use did not cause this problem) or the factory was aligning the ground glass improperly based on who knows what? People have sold their old Bronicas because they could not get truly sharp photos, which should have been possible with the good Nikkor optics. I assumed this problem was the finder foam only. Now I know better. Once again, this type of problem is what scared Nikon originally when they first made their great lenses available for Bronica 6x6 cameras. That something would go wrong in the focus system of the camera and given their lenses a bad reputation. That is why the original Bronica Z/Deluxe had a back with a film flattening device. Maybe contributing to why the early cameras are hand made and most have fine precision tolerances. I got into this study as I recently adapted a 180MM f2.8 Zeiss Jena Sonnar to my Bronicas. This unit focuses past infinity, so I must be sure the cameras are properly aligned to get sharp photos wide open at f2.8 at infinity or any focus setting. I can now do this on the "C" and "S-2". If you have several backs you should check the back focus on all of them as some backs may be out of focus specs.

On my tests on Bronica C, S-2 and S-2A: I have found the film sometimes bows very slightly into the aperture [Ed. note: e.g., bulging towards the front of the camera and the body cavity] - this varies with each camera, back and which exposure is on the roll. It is a sometimes minor medium format problem that generally has no solution - for precise work, depth of field will have to be used if this is a problem. In my tests, the Bronica "C" with the fixed back shows the least degree of this problem. I read that these were used for microscope photography and they may have a greater degree of focus precision with the fixed back. Don't throw your S2-A away because of this- it still can work well. This fact of the film bowing into the aperture proves that the film will mainly be at infinity in the aperture, very slightly in front of infinity if bowing into the aperture, but possibly mever past infinity where the ground glasses I tested were - unless a defective back was used. Critical focus problems on Medium Format are not just a Bronica problem. Rollei and others have made backs and matched inserts. And, Hassy and Rollei 6x6 SLRs generally have many lenses with top apertures of only f4 and f5.6, while Bronica has had wider aperture lenses. Part of the reason for smaller aperture lenses may be to encourage stopping down to cover any minor focus problems that depth of field will conceal. What has really amazed me is the precision with which my later model Bronica Deluxe was made. This camera always focused crisp exactly at infinity on the finder ground glass with its precision focus knob. The groundglass is locked in position with 4 screws, so it it had any foam which deteriorated the groundglass could not move in any event. I have used this camera with 300MM f5 Komura, which I adapted to the camera, and which focuses past infinity- with sharp results all of the time. Treat all of the old focal plane Bronicas with care, have them properly aligned, and with fine Nikkor and other lenses they are still capable of the best in medium format work. - Sam Sherman

From Bronica Mailing List: Date: Wed, 03 Nov 1999 from: [email protected] Subject: BRONICA S2-A: Important Focus Tip from: [email protected] (Sam Sherman) 11-3-99 to: Bronica ListThe challenge is on. Can Bronica S2-A take pictures as sharp as Hasselblad can?

I say yes! But, can I prove it? I have been improving the focus on my Bronica S-2A, S-2 and C models over the last several months see focus information on Bob Monaghan's Classic Bronica website Here is my latest sharp focus tip: For Bronica S2-A, S-2, C, some "S" models and possibly EC, ECTL and ECTL II (if they have similar inserts) The film Inserts in the 12/24 and 16/32 (120/220) backs need watching. Their positions in the camera are vital to Sharp Focus. 1- Remove the Insert and examine it carefully. Sometimes screws on the side loosen up, especially chrome ones on the bottom roller.This impedes the Insert from locking tightly into the back. Take a proper small screwdriver and tighten these and all the screws on the insert, whose vibration will loosen them over time. 2- Now clean the rubber rollers which connect to the counter. I use a small amount of Nail Polish Remover (acetone) on a Q-Tip with paper sticks, not plastic ones which dissolve. Then go over these rollers with the dry side of the Q-tip. Be careful that the roller on the left aide away from the counter gears is not slipping. It is mounted on a metal wheel that has a notch where you can put a screwdriver in to tighten it. Next clean the whole Insert without solvent (unless it is filthy) and be ready to test putting this Insert in the camera back. 3- Replace the Insert in the back and press on the central bar where the two locking handles are (the ones you squeeze to the center to remove the Insert) - press on this bar with your thumbs and watch that both side prongs solidly lock into the back. 4- If they do not and have sluggish action remove the Insert. The prongs on the side of the Insert and the locking handles in their shafts may each need a small drop of very light lubricating oil. Then exercise these handles to be sure they work smoothly. 5- Replace the Insert in the back using your thumbs to press it in. It should work fine. If not, study it for other problems of alignment, bent parts etc. If unfixable it may need to be replaced. THE PROBLEM IS: the Insert will appear to lock in the back with ONE only of the locking prongs really locked in, or NEITHER of the locking prongs locked in. If not properly locked in one can hear the wind gears lightly grinding as there is imcomplete contact between the camera winding gears, the back gears and the insert gears. In this case the film will also not be locked in right at the camera aperture and is a little behind or rippling- not flat.

THE FOOLER: The Insert appears to lock in, but is not fully locked on one side. One side of the film will not be pressed as far forward as it needs to be and can be slightly or more out of focus. Once you have worked on the Insert - Practice locking the Insert solidly in the camera back and notice how the locking handles both have moved out to each side, indicating the prongs are out and locked in the back. Study this carefully! This is a tricky matter I have never heard discussed before, but it results in improper operation of the camera, not as it was designed to work......... and less than Sharp Focus. Once this works properly, you will be taking another step to Sharper Pictures. - Sam Sherman

From Bronica Mailing List: Date: Thu, 04 Nov 1999 from: [email protected] Subject: Old Film Inserts Could Be Trouble from: [email protected] (Sam Sherman) 11-4-99 to: Bronica List In followup to my previous post regarding use and maintenance of Bronica Film Back Inserts for Bronica S2-A, S-2 and C. (Note: the Bronica EC and ECTL, ECTL II uses the same or a similar insert even though the backs differ from the earlier models) These later models have two white lines on the Insert to show what position the two locking handles should be at when the Insert is properly locked into the back. Failure of the Insert to lock in completely into the back (prongs in sockets on both right and left sides) can definitely cause winding and soft focus problems. Original Bronica Factory Instructions for Models S-2 and C do not emphasize the importance of locking this type of Insert (new at that time) solidly into the back. Original Bronica Factory Instructions for Model S-2A, ECTL (and possibly EC and ECTL II) do emphasize the importance of locking the Insert properly into the back. These instructions do not fully detail the problems improper use can cause, but after having some experience with these Inserts after the passage of several years, Bronica was well aware of the problems the Inserts were capable of causing with improper use. Properly used - these Inserts are a good product, well made and capable of excellent performance. - Sam Sherman

see How to replace the deteriorating foam on your camera. by Glenn Stewart see Gasket Repairs on Medium Format Cameras See Fargo Enterprises for foam and camera repair manuals and tool resources...

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