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Yashica GSN Light Leak
Old 07-07-2011   #1
ColSebastianMoran
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Yashica GSN Light Leak

Found a light leak in one of my GSNs. A few pictures looked a little 'bright' and might have passed inspection. A diffuse light leak can look deceptively like over exposure.

So, I created a test. Fresh film. Shot a couple of frames. Then advanced four blank frames and put the camera in a brightly lit area for a day. The results are surprising and very clear. I'll post examples first and then the strip of test negatives.

Here's the first example. Light leak, or just a little bright in the left center? I found it hard to tell.

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Old 07-07-2011   #2
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Then, a little further in the same roll, I began to see clearer evidence. I found a two-frame sequence that repeated a couple of times. It was from a winter day out in very bright sun. Camera on neck strap, no case.

Here's the first of the two-frame sequence. Light leak.

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Old 07-07-2011   #3
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And, here's the second piece of the two-frame sequence. I found this same sequence a couple of times in the roll.

Light leak, yes. A diffuse leak in the center (vs. the left) and a distinct line. That's the second frame, different from the first. I think it would be hard to figure this out just from the frames I've shown.

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Old 07-07-2011   #4
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I'm the experimental type. So, I designed a test to find the leak. Fresh film. Shoot a couple of frame. Then run past four blank frames to put unexposed film in all the areas of interest. Then leave the camera in bright light for a day. Click off four more blank frames to avoid exposing over any further leaks, and inspect the whole negative strip.

Here's the film strip:



And, here's some explanation:
- Right hand side is the film leader. It's bulk loaded so Kodak's frame numbers are meaningless.
- A couple of correctly exposed frames of test targets. These look fine.
- Note light leaks at the edges. I've determined that these are from my bulk-loaded film and appear with all my cameras. I'll worry about these later.
- For the full-day test in bright light, Frame 7 is in postion behind the lens.
- I believe A is the primary leak, onto the take-up spool. Looking at the camera geometry, it's from the film-door hinge. GSN winds film on the take-up spool with emulsion out. Nice broad light leak.
- B is print-through of sproket holes at A onto the film one layer down on the take-up spool.
- C is confusing, especially the distinct line. This is on film at or near the advance sproket. Is this light through the anti-halation backing? Why the line? Electro owners, please have a look inside your cameras and see if you can figure out what creates this pattern.
- In this test strip, everything beyond Frame 7 is clear, so there's no further light leak.

Solution: Added a second piece of light seal at the film-door hinge. This solved the problem.
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Old 07-24-2011   #5
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Oh yes that would solve the problem ... i have just experienced almost exactly the same thing with my mint GSN. A very close look a the seals told me that it was time for new foam ... if only I had looked at the foam before i shot 2 rolls of film. Like you i got some good shots and blown ones, guess the ones without the leaks i was holding the camera tightly and keeping the light out or maybe i had my hand covering the area where the light seals were gone.
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Old 07-24-2011   #6
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Quote:
Originally Posted by bgb View Post
... Like you i got some good shots and blown ones, guess the ones without the leaks i was holding the camera tightly and keeping the light out or maybe i had my hand covering the area where the light seals were gone.
Or, maybe it's the time between shots for the light leak to accumulate exposure. Remember for the leak at the door hinge on a GSN, the frames that are ruined are two-ahead and one-ahead of the frame that's behind the lens.
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Old 07-24-2011   #7
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yes maybe ... i was using mine on a very sunny day. The first roll i ever took was in winter and no leaks at all.
It's on the bench in front of me getting the foam replaced now !
Foam was completely shot
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Old 06-03-2012   #8
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Quote:
Originally Posted by ColSebastianMoran View Post


...
- C is confusing, especially the distinct line. This is on film at or near the advance sproket. Is this light through the anti-halation backing? Why the line? Electro owners, please have a look inside your cameras and see if you can figure out what creates this pattern.
...
Another thread got me thinking about this leak again. The open question is what is the distinct line, the lighter vertical line in the positive image #3 above, and the dark narrow vertical line in the negative (just left of the dark area "C").

All this comes from a big light leak through the door hinge. I now think the narrow vertical line is the leaked light reflecting off the edge of the pressure plate.
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