A note up front. This article describes a camera repair I did at a point when I was a fairly inexperienced fixer. I have since done more work on this and other cameras (the later piece on the same camera’s focusing screen saga covers the second round, several months later) and I have learned a lot in the process. The story below is honest, including the bit where I scratched the fresnel screen. The takeaway is that this is a fix worth attempting yourself if you have the right foam and a steady hand. The fresnel scratch was avoidable. Read on.
The problem this article is about is one of the most common issues with Bronica S2 and S2A medium format cameras. The symptoms are subtle at first and genuinely maddening to diagnose. The fix is straightforward (replace some degraded foam) but the foam is in a location that requires partial disassembly of the camera to access. This is the writeup of doing it.
The symptoms
If you have a Bronica S2 or S2A and you have noticed any of the following, your foam has degraded and your focus is off:
The focus on close subjects is consistently a bit soft. You compose carefully, you focus precisely on the ground glass, you fire the shutter. The negative comes back with focus that is close to where you wanted it but not quite on the eyes (or wherever you put the focus point). Sometimes the focus is forward of where you intended, sometimes behind, sometimes both depending on how close the subject was. The pattern is not random; it correlates with subject distance.
The camera cannot reach infinity focus on distant subjects. You set the focus ring to the infinity mark on the lens. You compose a frame of a distant landscape. The ground glass tells you nothing is in focus. You assume the lens needs adjustment or the focusing screen is wrong. In fact, the ground glass is lying to you.
You sometimes get sharp frames by chance and sometimes get soft ones, with no pattern you can identify. This is the most common version of the problem. The camera is broadly working but unreliable. Some frames come back nicely, others are slightly off.
All three symptoms point to the same cause. The foam under the ground glass has degraded, which has caused the ground glass and fresnel stack to drop by a fraction of a millimetre. The ground glass is no longer at the position where the camera was designed to put it. The image you see on the ground glass is no longer an accurate representation of the image hitting the film.
Why this happens
The Bronica S2 and S2A use a sandwich of two optical elements (a fresnel lens and a ground glass) sitting on top of a pair of leaf springs in the camera body. Foam strips around the perimeter hold the stack in place and cushion it against vibration. The waist-level finder clips down over the top, pressing the whole assembly into position.
When new, the foam holds the stack at a precise position. The matte surface of the ground glass sits exactly where the camera’s optical design says it should sit. The image projected through the lens forms perfectly on the matte surface, giving you an accurate ground-glass preview of what will hit the film.
Over time (and we are talking decades here, since most S2 and S2A cameras are now 50+ years old), the foam degrades. It loses its springiness. It compresses under the weight of the waist-level finder. It eventually breaks down into a gummy black residue that sticks to everything it touches.
When this happens, the ground glass stack drops by a small amount (half a millimetre to a millimetre, depending on how compressed the foam has become). The matte surface is now slightly below its designed position. The image still forms in the same place optically, which means the matte surface is now slightly above the true plane of focus. You focus by looking at the image on the matte surface, but the actual sharp image is forming above the matte. Your eyes see “sharp” before the focus is actually there.
The size of the focus error depends on the distance to the subject and the focal length of the lens. For a typical Bronica 75mm lens at infinity focus, half a millimetre of screen displacement equates to a focus error of 30 to 60 metres at the subject. The lens cannot physically reach focus beyond its infinity mark, so you simply lose the ability to focus on anything more than 50 to 100 metres away.
For close subjects, the error is smaller in absolute terms but more noticeable because depth of field is shallower. Half a millimetre of screen displacement at a 2-metre portrait distance means the focus is 5 to 10 centimetres off where you thought it was. Right on the eyes becomes right on the ears. Crisp focus becomes soft focus.
This is, in summary, an age-related calibration problem caused entirely by a perishable material that has perished. Fixing it means replacing the foam.
The fix, in principle
To replace the foam, you need to:
- Remove the waist-level finder from the top of the camera.
- Remove the four small metal screws that hold the focusing screen frame in place.
- Lift out the focusing screen assembly (which contains the ground glass and the fresnel).
- Scrape out the degraded foam.
- Clean the surfaces.
- Apply fresh foam strips around the perimeter where the old foam was.
- Reinstall everything.
- Test infinity focus to confirm the fix worked.
The whole job takes about an hour if you have the foam ready and you do not lose any of the small screws. None of the steps require precision tools or specialist knowledge.
What you will need
- A small Phillips screwdriver that fits the four metal screws (a precision screwdriver set is ideal; I used one of the Wowstick-style electric ones in the video)
- Replacement foam (more on this below)
- Isopropyl alcohol and cotton buds for cleaning the old foam residue
- A small wooden or plastic poker for nudging things into place (do not use anything metal)
- White cotton gloves to avoid fingerprints on the optical surfaces
- A clean, well-lit work surface
The foam is the critical part. You want closed-cell self-adhesive foam in a thickness of around 1.5 to 2mm. Mine was sourced from HGL Group on eBay (a UK supplier of camera repair foam in various thicknesses) and worked well. The foam should be wide enough to fit in the perimeter channel (around 10mm wide is good) and long enough to do a full perimeter strip (most strips are sold by the metre).
If you cannot find the right thickness, you can layer thinner foam or trim thicker foam to size. I confess in the video that I started the job with 10mm-thick foam (intended for a different purpose entirely), trimmed it down with a knife to roughly the right thickness, and used it anyway. The 10mm foam was clearly too thick. The job still worked. But the right foam from the start would have made it much easier and the result more precise.
If you are reading this and you are about to do this job, wait for the right foam to arrive before you start. I was impatient. You should not be.
The actual repair (with mistakes)
I followed the instructions from a Russian camera fixer’s site at goroshilov.com, which is the best reference I found online for this specific job. The instructions are clear, illustrated and accurate. Recommended.
Step 1: Remove the waist-level finder. There is a small tab on the back of the finder that you lift upwards with a fingernail. This retracts a small spring clip and releases the finder from the camera body. It lifts straight off. (Mine had become slightly over-extended over time, with the rear half not sitting flush with the sides. This is a separate small fix that I did not address in this video.)
Step 2: Remove the four screws. Four small metal screws hold the focusing screen frame in place. They are visible once the waist-level finder is off. Use a screwdriver that fits them precisely. Stripped screws are a nightmare to deal with on a vintage camera, so do not over-torque.
Step 3: Lift out the screen. With the four screws out, the focusing screen assembly lifts straight up. Inside, you should find the fresnel lens (the ribbed plastic disc with the concentric rings) and the ground glass (the frosted glass surface). These sit on two small leaf springs that push them upward against the frame.
This is where I scratched the fresnel.
Picking up the assembly, I touched the fresnel surface with my finger. Then in trying to clean off the fingerprint, I slid a fingernail across the surface, leaving a small scratch about 5mm long on the edge of the ribbed surface. The scratch is in the corner where it does not affect viewing in normal use, but it should not have happened. The ribbed surface of a fresnel lens is delicate. Any abrasion against it causes permanent damage. White cotton gloves are not optional for this job; they should have been on my hands from the moment the screen came out.
Lesson learned. Wear the gloves. From the start. Do not touch the optical surfaces with bare fingers.
Step 4: Inspect and clean the old foam. What I found under the assembly was grim. The original foam had degraded into a black gummy residue that had spread across the inside of the frame and the underside of the ground glass. Some of it had transferred onto the matte surface of the ground glass itself, which is the absolute worst place for it to be. The gummy residue smears across the surface and is hard to remove without further damage.
I cleaned the foam residue off with isopropyl alcohol and cotton buds. This took longer than the rest of the job combined. The black gunk does not come off easily. Multiple passes and lots of cotton buds are required, plus a careful hand. The ground glass itself I cleaned with a lens-cleaning cloth and isopropyl alcohol, which got most of the residue off. The fresnel was harder because the ribbed surface traps residue between the ridges; I cleaned what I could see and accepted that some would remain in the troughs.
Step 5: Apply new foam. I cut strips of my 10mm-thick foam down to roughly the right thickness by hand, which produced wonky strips of varying dimensions. I applied them around the perimeter of the frame where the old foam had been, pressing them down to engage the self-adhesive backing. The result was visibly uneven (my strips were not the same thickness anywhere, let alone consistent around the perimeter) but I trusted that the compression force of the waist-level finder pressing down would even things out when the assembly was reinstalled.
Step 6: Adjust the springs. The instructions said to bend the two leaf springs upward by a small amount to ensure they had enough tension to hold the fresnel against the new foam. I did this gently with a non-metallic tool. The springs are soft brass and easy to bend, and the amount required is tiny.
Step 7: Reassemble. Fresnel first, ribbed side up, sitting on the springs. Ground glass on top of the fresnel, matte side up. (I got this wrong on the first attempt by trying to sit the ground glass on its own on the springs without the fresnel underneath, which is incorrect. The two pieces go together as a sandwich.) Frame back over the top, with the foam compressing as the screws go in.
Step 8: Screws back. Four screws back into their original locations, threaded in carefully by hand first to avoid cross-threading, then tightened to a moderate firmness. Not over-tight. The foam needs to compress, but you do not want to deform the frame.
Step 9: Waist-level finder back on. Slid into place from the front, with the rear spring clip engaging as it dropped down. Click. Done.
The test
I took the camera over to the window and pointed it at a tree about 40 metres away. With the lens set to infinity, the tree should be in focus on the ground glass.
It was. In focus, sharply. Crisp. Sharp. The first time I had seen distant subjects properly focused on this camera since I had bought it months earlier.
I pointed at a closer subject. About 5 metres away. Focused the lens. Looked sharp. Then pulled focus past it and back to confirm I could see the focus go in and out as expected. It did. The ground glass was now showing me an accurate representation of the focal plane.
I would not know for certain that the fix had worked until I shot and developed a roll of film, which I did the following weekend. The frames came back sharp. The fix worked.
What this teaches you about working on vintage cameras
A few things from doing this job.
The foam in any vintage camera is suspect. Bronica S2 and S2A models are 50+ years old. Every piece of foam in every example currently on the second-hand market is past its design life. If your camera shows any symptoms that could be foam-related (light leaks, focus problems, mirror slap, sticky shutter), foam is the first thing to suspect.
Replacing foam is one of the easiest fixes available. Compared to shutter timing or meter calibration or rangefinder adjustment, foam replacement requires no special tools and no specialist knowledge, with no service manual needed. It just requires patience and clean working conditions.
Wear the gloves. Cotton gloves cost about £3 for a pack of 12. Wear them whenever you are inside the camera. The scratch on my fresnel would have been avoided if I had been wearing gloves from the start.
Use the right foam thickness. Do not bodge it like I did. Order the right foam. Wait for it to arrive. The job is significantly easier and the result better.
Read the instructions before you start. The goroshilov.com walkthrough I followed was excellent and detailed. I would not have known where to start without it. There is no shame in following someone else’s instructions on a job you have not done before.
Bronicas tolerate amateur intervention better than most cameras. Unlike a Leica or a Hasselblad, the Bronica was built robustly enough that an enthusiastic amateur with basic tools can disassemble and reassemble parts of it without breaking anything. This is part of why I have grown so fond of these cameras. They reward people who want to keep them working.
What comes next
The fix from this video held for a few months. Then it stopped holding. The foam I had used (the wrong thickness, bodged together) compressed further over time, and the focus problems returned. The story of what I did about it, including buying an aftermarket Brightscreen and creating a whole new set of problems, is covered in the focusing screen saga from a few months later. That piece concludes with me eventually reinstalling the original Bronica screen on fresh foam (the correct foam this time) and finally getting the camera working reliably.
If you are doing this job for the first time on your own Bronica, save yourself the second round. Order the right foam. Wait for it. Do the job once, properly, with the right materials.
If you have done this fix or want to share your own experiences, the comments are open. There is a small community of Bronica enthusiasts keeping these cameras running, and the wisdom passed around in those communities is what kept me out of trouble (mostly) on this and other jobs.