(PCS) Excellent mechanism, Bronica S2…but why infinit focus is not correct?

Problem Description

Many of old Bronica, focal plane S series have infinite focus problem now. (Bronica type Z, D, C, S, S2, S2A)

If your Bronica has accurate focusing, either workshop or previous owner take action already to fix this problem, most likely.

(And you are lucky…)

Checking method fot the issue is simple. Just place the lens to infinite position and aim far distance subject.

Image on the screen may awfully defocused if the Bronica has this problem.

Or find out a subject at known distance (for example 1m), focus and read distance on the lens. It may show 50cm or so…

I mean, if infinite problem occurred because of the reason described below, distance offset is significant amount, not slight…

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1. Fresnel lens  2. Focus screen holder     3. Focus screen      4. Finder hood

Root Cause

Bronica S design has unusual focus screen structure. There is 1 pair of leaf spring to lift whole screen glasses upward.

Then sponge (form) push down the screen to touch the metal plate (registered distance) to make infinite focus accurate.

If sponge degraded and can not push down firmly, the screen glass lifted from registered plate, thus lost focusing reference completely..

Now, after 40-50 years after Bronica production, surely those sponge degraded already….

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Leaf spring to push up screen mechanism

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Original sponge degraded and melted. Has to clean it carefully

Solution

If root cause is the sponge, replace with new one will solve the problem. Right?

Question is what kind of sponge we need to use?

There is no way to get genuine Bronica sponge any longer, all kind of creative ideas used, from kitchen tower to recycled

sponge from children’s toys. There are couple of forums dedicated to this subject in the internet….

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Focus screen and screen holder need to be cleaned thoroughly too..

Good news is there are ready made alternatives.

Some persons sell bright screen for old SLR camera as DIY through internet including Bronica S2.

Compare to latest SLRs, old SLRs has dark screen even when new, and now they become even darker.

So there is small but nitch market for film camera users to replace old dark screen to new one.

One of those seller offers ‘bright grid split-prism screen’ together with replacement sponge for Bronica.

… I am thinking now ordering new bright screen, or just clean and find something creative for sponge.

TO BE UPDATED

(PCS) 브로니카 S2, S2A 에서 가장 중요한 부분 - 포커싱 스크린 폼 : DSC05089 650.jpg

글쓴이 Leo_KHIMME

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