Weird light leak from black plastic bulk load cassettes

[railwayman3]

That's literally the only thing I can think of, yeah. But what I don't get is why it's that pronounced only on specific frames. My working theory now is that somehow, light from the viewfinder (or lens) that normally gets into the camera and is blocked by the felt on commercially loaded canisters somehow wasn't by these. I'm going to double check when I get home, but I have a theory that it's going to be more pronounced on frames that were shot when I was outside in bright sunlight, and that the darker ones are on frames where the film "sat still" inside the camera. If I took several frames in quick succession, I'm thinking those are the ones that are okay.

That was the sort of suggestion that was coming to my mind as I read through the thread, i.e. some very small light leak, not sufficient to affect a frame when it passed through the camera quickly, but sufficient to build up to cause fogging where the film sat still in the camera during breaks in shooting...particularly if the camera were in bright sunlight.

 

[shutterfinger]

It's not the camera (a Canon A2E)

Ah, but it is.
Its not compatible with the plastic cassettes, OR the light seal around the cassette window is worn just enough that it seals well around a metal cassette but does not seal against a plastic cassette.
Those windows over the cassette are a potential source for light leaks and should be blocked off to prevent light leaks. Strong side lighting can leak in even with good window light seals.

 

[lifein2x3]

Ah, but it is.
Its not compatible with the plastic cassettes, OR the light seal around the cassette window is worn just enough that it seals well around a metal cassette but does not seal against a plastic cassette.
Those windows over the cassette are a potential source for light leaks and should be blocked off to prevent light leaks. Strong side lighting can leak in even with good window light seals.

Point taken. And now that you mention it, that's most likely the culprit. I typically keep my camera slung over my left shoulder with the lens pointing down, which puts that window facing the sun. So as I was walking around San Francisco, light was leaking through that window and the canister building up fog. That makes more sense than anything else I've got.

 

[ic-racer]

t's obvious the problem is the plastic cassettes...

Throw out the bad cassettes, get some new ones. Don't waste more than five seconds on this if you have figured it out already.

 

[lifein2x3]

So I've gotten home and gotten the negatives into sleeves. Here are some of the worst leaks. One pattern I've noticed is wherever the weird "UFO" leak appears, it's always below one of the large block leaks. The denser the block-shaped leak, the darker the "UFO" streak.

 

[Kirks518]

shutterfinger hit the nail on the head.

The 'UFO' is the little window on the pressure plate. Light is coming in from the canister window, exposing the closest 1/3 of the frame, and light is also getting in behind the pressure plate and sneaking through the date stamp window to make the UFO.

Nothing a little foam seal won't fix. Might as well reseal the whole back. If you're really lazy, you can just cover the canister window with black gaffer's or electrical tape.

 

[Xmas]

shutterfinger hit the nail on the head.

The 'UFO' is the little window on the pressure plate. Light is coming in from the canister window, exposing the closest 1/3 of the frame, and light is also getting in behind the pressure plate and sneaking through the date stamp window to make the UFO.

Nothing a little foam seal won't fix. Might as well reseal the whole back. If you're really lazy, you can just cover the canister window with black gaffer's or electrical tape.

The backs I've seen have foam seals from the factory if there is a little groove around the window that is looking suspicious you need to inspect if there is a groove around the window then there may be other areas missing foam.

Mr Lazy may have replaced the foam...

 

[lifein2x3]

The backs I've seen have foam seals from the factory if there is a little groove around the window that is looking suspicious you need to inspect if there is a groove around the window then there may be other areas missing foam.

Mr Lazy may have replaced the foam...

Nope. The light seals are fine. If they weren't, surely I'd've had problems on the 20 or 30 other rolls of film I've put through the camera since getting it last year?

I'm just going to chuck the plastic ones and replace them with metal cassettes. I've used that type for over a decade without any problems.

 

[lifein2x3]

shutterfinger hit the nail on the head.

The 'UFO' is the little window on the pressure plate. Light is coming in from the canister window, exposing the closest 1/3 of the frame, and light is also getting in behind the pressure plate and sneaking through the date stamp window to make the UFO.

Nothing a little foam seal won't fix. Might as well reseal the whole back. If you're really lazy, you can just cover the canister window with black gaffer's or electrical tape.

You know, looking at the cassettes again, I may have found the culprit. I used a label maker to label them (because anal-retentive organization is my thing.) Said label maker uses 1/2" white tape.

Shiny, high-gloss, white tape.

::headdesk::

 

[Kirks518]

I'll bet the seal isn't good. It may look good, and it may feel good, but it's probably compressed with age, and the plastic cassettes may be a teensy weensy bit smaller then metal cassettes. Replace the foam, or cover the window, and you'll be good to go.

Hold up one of the bad frames the back so that the 'UFO' matches the oval shaped window, and you'll see the other affected area will match up to just one side of the foam around the cassette window.

I doubt the label has much, if anything to do with it. If the seal(s) were good, you could put a mirror in there and it wouldn't affect anything. But your seals are not good...

 

[lifein2x3]

I'll bet the seal isn't good. It may look good, and it may feel good, but it's probably compressed with age, and the plastic cassettes may be a teensy weensy bit smaller then metal cassettes. Replace the foam, or cover the window, and you'll be good to go.

Hold up one of the bad frames the back so that the 'UFO' matches the oval shaped window, and you'll see the other affected area will match up to just one side of the foam around the cassette window.

I doubt the label has much, if anything to do with it. If the seal(s) were good, you could put a mirror in there and it wouldn't affect anything. But your seals are not good...

I guess the way to test it (because now I have to know) would be to try a plastic cassette outside in sunlight without the tape, one with the tape, and one of the metal cassettes. Shoot a couple of frames on each roll with tape over the window, and a couple of frames without it. If it ends up being the window, a piece of electrical tape should do the trick. I've got a few RB67 film backs that need new seals that are a higher priority than this camera.

 

[Xmas]

Well the window can be useful but they normally have a compliant foam surround to prevent a leak, you need to google

jon goodman foam

For your cameras instructions.

As well if the rest of the foam is in any way not as new you need to replace before any bits migrate into your shutter mechanism. That would be bad.

RB backs take ages.

 

[Archone]

I've actually seen something like this before about thirty years ago. It was with the plastic loader on a lloyds bulk roller. Anyway, the plastic cassettes I was using didn't have very good felt. So if I stored them in the clear Fuji canisters instead of the black Kodak ones, a stripe similar to yours would appear. Took me a while to figure it out as it would only happen when I loaded the camera in daylight. But sure enough, upon careful inspection of non daylight loaded film, there was a light fog in the same pattern.

Swore me off from the plastic canisters forever. I only use the metal ones now.


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