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05-28-2017, 08:50 AM   #1
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Help finding the source of this light leak

Hello everyone,

I am in a bit of a Sherlock Holmes case of light leak, and I hope you can help me find the source of it.

I belong to the digital generation but I decided to embrace film and learn the origins and heart of the art. So, I bought a fine PZ-20 / Z-20 camera, second hand of course, but it's in very good conditions. I wanted to use my 35mm DAL and 70mm Limited primes and I needed a camera capable of handling them.

First thing I did when I received the camera was to check for the light seal, it had none. I'm still not completely sure whether the camera needs one or not, but anyway, I bought 1mm thick felt fabric and carefully cut a seal to match the door pattern. Now the door closes snugly and without forcing the hinge. There are a couple of pictures below.

The next thing I did was to load an AGFA CT Precisa 100 color reversal film, that I know is very picky with the exposure and checked all my shots against my light meter. I took some test shoots in a sunny day and it seems that the camera does not have problems nailing the exposure.

Finally I received the developed film, but almost all the photos had these vertical burns. There is also a small rectangular burn between frames 9 and 10 that I think might be the door window. There are some pictures below.

I bought another roll of film, so I have to think carefully on a set of tests that can solve the mystery.

Any help or suggestion is really appreciated.

Thanks!

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05-28-2017, 09:14 AM - 1 Like   #2
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Here's a quick trouble-shooting test:

Place that strip of ruined film against the back of the opened camera (with the image upside down, the emulsion facing the lens, and one of the image frames centered in the gate). Then look at where the ruined parts lie relative to the canister side and the take-up spool side.

My guess is it's hinge next to the take-up spool because the leak seems to be coming from the side across the entire width of the film rather than being predominately from the top or bottom.
05-28-2017, 09:29 AM - 1 Like   #3
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You may want to consider taking out the felt. Looking at the design of the back and body, they may have just used baffles for a light seal. By adding the felt, you may be keeping the camera from locking tightly now. IS the camera back hard to close? If so, this might be an indicator.

Second, try going through exposures quickly, THis may be a situation where the leak is minor, except over time.

Good luck!
05-28-2017, 11:21 AM   #4
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Take the lens out, fire the shutter in B mode without film and back cover closed. With a light behind, look through the mirror box to trace the leak!

05-28-2017, 12:45 PM - 1 Like   #5
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Based on the angle of the sprocket hole light leak direction, the width of the leak, and the felt edge like pattern on one side, I would guess the leak is coming from the film canister window on the inside back door. The light is centered but spreads outward from the source as seen in the sprockets. Itʻs hitting the film that is just outside the canister.

The simplest solution for your test (if Iʻm correct) is to make that window completely opaque with tape.
05-28-2017, 03:43 PM - 1 Like   #6
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Thank you very much for all your help!

I tried Photoptimist suggestion and put the film against the back of the opened camera, and it supports the hypothesis of Alex654: on the side of the film canister, the burn has the same width as the space between the pressure plate and the canister border. There is a figure below.

I also tried RuiC suggestion, with a flashlight from the lens mount side in a dark room, and the only place I could see light was from the window. Nowhere else.

BigDave, I don't feel the door hard to close, the difference is subtle though. Without the felt, the door moves sideways a little bit, with the felt it doesn't. I can take the felt out and make a test, it is not glued.

Tomorrow I will load a 400 ISO film and take the camera out, under the bright sun. With the lens cap on I will try:

1) Window uncovered.
2) Window covered.
3) A couple of quick shots.
4) Leave one frame in place for a long time.
5) Shooting with different parts of the door taped.

Unfortunately, the film development takes 10 days, but as soon as I receive the photos I will let you know.

Thank you very much!.
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05-28-2017, 04:22 PM - 2 Likes   #7
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You need to turn the film strip over, it needs to be upside down. (Top of the image to the bottom of the camera)
05-28-2017, 06:20 PM - 1 Like   #8
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I think the Z-20 is basically the same as the Z-50. If so, it doesn't need conventional light seals and, as BigDave said, the felt may be stopping the back from closing tightly. There's just a couple of very tiny strips of foam, about 1/4 of an inch long, in the corners by the hinge, and the usual foam around the film canister window.

05-29-2017, 02:12 AM - 1 Like   #9
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QuoteOriginally posted by Suzhouren Quote
I think the Z-20 is basically the same as the Z-50. If so, it doesn't need conventional light seals and, as BigDave said, the felt may be stopping the back from closing tightly. There's just a couple of very tiny strips of foam, about 1/4 of an inch long, in the corners by the hinge, and the usual foam around the film canister window.
Agreed. There's only the seal around the film window and a very small seal at the top of the door, and some tiny ones near the hinge. Z-10 is identical. I think, as a first step, you need to remove what you have added and re-test.
05-29-2017, 06:29 AM   #10
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Thanks! Suzhouren and MarkJerling. Ok. The first test would be then: no felt and film window covered.

What I could not find was a position of the film inside the camera in which the image is upside down, facing the curtains, and the first frame being the one getting first into the take-up spool.

I will do the test and see what happens.

Thanks again!

05-29-2017, 01:39 PM - 1 Like   #11
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I attach two photos for you of my Z-10 showing where it has felt. As you can see, there's not very much of it. And the felt that is there is quite thin.
I've deliberately lifted the dark areas in PS so as to show more detail on the black surfaces.
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05-30-2017, 08:04 AM   #12
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QuoteOriginally posted by Hyperfocal Quote
Unfortunately, the film development takes 10 days
Wow! Remember when there were one hour photo processing businesses? Talking about going backwards!

Good luck. I think you are going to get this one solved.

Regards,
05-30-2017, 02:40 PM - 1 Like   #13
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QuoteOriginally posted by BigDave Quote
Wow! Remember when there were one hour photo processing businesses? Talking about going backwards!

Good luck. I think you are going to get this one solved.

Regards,
Wow, yes, but I was too young. Never did it myself. I know of a lab that can do the job in just 3 days, but I would need to drive 70Km... or send the rolls by mail. Still many days if you take into account the post.

Thank you very much MarkJerling! Now I can replace the seals, and just in the right position. The felt I have is quite thin, 1mm uncompressed.

Finally, I've found the position of the film in the camera. On the left side it is still in the same position, between the pressure plate and the cartridge; on the other side, it goes far to the right of the take-up spool.

Tomorrow I'll receive a fresh roll for the test. I'll post the results. I hope someone could find it useful. Let's see how it goes. BTW, is Amazon a reliable place to buy the films? I've read that it is important to ensure the rolls don't go through the cargo x-rays. Any surprises?.
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05-30-2017, 04:59 PM   #14
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I'd try it without adding anything and see how you go with that.
06-15-2017, 01:56 PM   #15
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I've just received the developed negatives from the tests I did. The source of the leak was... the door's window.

It was just a matter of covering the window with a black insulating tape.

Thank you very much to all of you, I really appreciate it.

Now I need to buy some serious film for my summer vacations on the beach :-)
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