Light leak/ development issue or something else?

Hi, I'm again on this thread because I can't wrap my head around the origin of this light leaks.
Further inspection the camera I noticed that the shutter travels from left to the right when advancing frame, as the film does, so I don't get how it can cast a light leak as this one. Am I wrong? could it be the that the light is coming from the prism / viewfinder area?

robonfilm said:

Further inspection the camera I noticed that the shutter travels from left to the right when advancing frame, as the film does, so I don't get how it can cast a light leak as this one.

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If the shutter travels from left to right, that would fit perfectly with length-wise light leaks on the negatives.

koraks said:

If the shutter travels from left to right, that would fit perfectly with length-wise light leaks on the negatives.

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Sure, but I still don't get how (or when) it can cast such a light during the operation of the camera: if the leak is due to curtains not overlapping correctly then it must be happening when film and shutter are advancing, but traveling alongside each other how can the light span from corner to corner and involve rebate and sometimes sprocket area?

robonfilm said:

how can the light span from corner to corner

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It doesn't span from corner to corner in the example you posted. It spans between and across the short edges of the negatives, so running lengthwise along the film.

robonfilm said:

involve rebate

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A light leak doesn't care where the image starts or ends. If there's a major problem with the shutter not being lightproof, then the fogging exposure will go all the way along the film, including the space between the frames.

robonfilm said:

sometimes sprocket area?

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You'll have to show an example, because the one you posted earlier doesn't exhibit this. Having said that, strong fogging exposure can bounce around/reflect in the film chamber. That would be one way it could also end up in the sprocket area.

In the above, I'm assuming that you have by now excluded all other possible failure causes inside and outside the camera except the shutter. Can you confirm this?

koraks said:

It spans between and across the short edges of the negatives, so running lengthwise along the film.

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It does. But how can it span like that if the light is coming from the overlap of the curtains? If the light is leaking when advancing the camera, would't it be more like a point on the negative (given that the negative and the shutter both travel from left to right)?

koraks said:

You'll have to show an example, because the one you posted earlier doesn't exhibit this

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As you can see, the frames that present the issue also have a distinct strike in the sprocket area :

koraks said:

In the above, I'm assuming that you have by now excluded all other possible failure causes inside and outside the camera except the shutter. Can you confirm this?

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I'm currently in the process of doing just that: I'm doing a test roll taping various parts of the camera and advancing the film with the lens cap on, taking note of which is which.

robonfilm said:

It does. But how can it span like that if the light is coming from the overlap of the curtains? If the light is leaking when advancing the camera, would't it be more like a point on the negative (given that the negative and the shutter both travel from left to right)?

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If the film is being transported, it will move behind any opening in the shutter. This can leave a smeared fogging artefact.
A point-shaped artefact would result from a small hole in a shutter curtain projecting onto the film as it's being held still.

robonfilm said:

As you can see, the frames that present the issue also have a distinct strike in the sprocket area :

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Yeah, that looks like severe fogging that just spreads out beyond the film gate. You can actually see reflections in that part that suggest an interaction with the edge of the film gate; note the thin, straight line that runs parallel to the image frame.

robonfilm said:

I'm currently in the process of doing just that: I'm doing a test roll taping various parts of the camera and advancing the film with the lens cap on, taking note of which is which.

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Sounds like a good approach; keep us updated!

robonfilm said:

Further inspection the camera I noticed that the shutter travels from left to the right when advancing frame, as the film does, so I don't get how it can cast a light leak as this one.

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The shutter probably advances faster than the film advances. So the gap between the curtains travels across an area of the film (which would include the space between frames). You don't have a "blob" of extreme density, so that implies the fogging occurs while these things are moving. When the shutter has been fired, the gap between the curtains is out of sight. When the shutter is cocked, it's also out of sight. It's while being advance that it can let light through to the film.

As for the light leak going into the sprocket area, look at the little point of high density down by your thumb at #28 and see how it blooms outside the frame. Reflections and light piping in the film itself - it's common for higher amounts of light to do that.

Don_ih said:

When the shutter has been fired, the gap between the curtains is out of sight. When the shutter is cocked, it's also out of sight. It's while being advance that it can let light through to the film.

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Yes, exactly!
The gap should be visible if the shutter is being cocked with the back open. If the advance lever is operated slowly, the gap should pass by slowly as well so you can have a good look at it.

The following suggestion is the best test, if you're uncertain.

Sharktooth said:

If there's a slit in the shutter that's occurring during winding then you could put a lens cap over the lens while winding.

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Take a couple of photos in bright light normally, then take a couple more with the lens cap on while advancing the film. You can take a couple more with the viewfinder covered, also, to eliminate that as a source of light. If there is no noticeable light leak with the lens cap on and the viewfinder covered, you know it's the gap between the curtains.

@Don_ih @koraks thanks as always for the useful suggestions!
If the shutter is actually the culprit I guess I'll always have to remember to advance te film keeping the lens cap on.
I'll run this test and will keep you updated.

I’m reviving this thread because I finally managed to solve the problem.

It turned out that the black light-sealing sleeve above the mirror box wasn’t properly tucked under the exposure meter cell. Because of that, some light was leaking inside.
After repositioning the sleeve correctly and reinstalling the meter cell, the light leaks are completely gone — everything’s working perfectly now.

Thanks to everyone who shared advice earlier! Hopefully this helps someone facing the same issue in the future.

That's great news. It's always good when you find the solution to a real mystery and everything works thereafter. Congrats!

Thanks for reporting back on the cause, great to hear you've been able to solve it!