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04-10-2021, 08:33 AM   #1
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Pentax 645N light leak - your thoughts?



Inevitably it happens once in a while. When testing a new purchase you find that it is not all it is supposed to be. In my case, it happened with my 'new' Pentax 645N. I recently shot a test roll, had the film developed and had it returned yesterday. Whilst the light metering - my biggest worry actually - was spot-on I also noticed at once that most of the shots were affected by light leaks. Most, not all. Out of a roll of 16, three shots were not affected and two only very slightly.

The other eleven shots all suffered from the same light leak as shown here. Now this puzzles me. I would have thought that all shots would have been affected. I used the 645N with the film magazine that was supplied with it. The lens I used was one I've had for years without problems. I used different aperture and shutter speed settings during the shoot. I am wondering what causes this. Is it the camera itself? The film back? If you've got an idea please drop me a line!

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Pentax 645N  Photo 

Last edited by Bas Stubert; 04-10-2021 at 09:48 AM.
04-10-2021, 09:29 AM   #2
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The film will show and tell. Can you print a straight contact sheet, light leaks can only come from so many places.


Hang up and DRIVE!
04-10-2021, 09:40 AM - 1 Like   #3
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QuoteOriginally posted by MikeMcE Quote
The film will show and tell. Can you print a straight contact sheet, light leaks can only come from so many places.


Hang up and DRIVE!
I gather that the photo doesn't appear automaticly? If you 'click to view photo' you'll see what happened. All images suffer from the same sort of leak.

EDIT: I've added an example as attachment.

Last edited by Bas Stubert; 04-10-2021 at 10:22 AM.
04-10-2021, 10:07 AM - 1 Like   #4
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the most common is the light seals on the film back, or failure to rotate the lock on the film back

04-10-2021, 10:36 AM   #5
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the contact sheet shows all, margins between frames. start with Denvers advice
04-10-2021, 12:27 PM   #6
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Is it in the same shape on multiple frames? Or a different position on each frame? Or just one part of the film.
Denver's advice is best first step.
04-10-2021, 12:47 PM   #7
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QuoteOriginally posted by ProfessorBuzz Quote
Is it in the same shape on multiple frames? Or a different position on each frame? Or just one part of the film.
Denver's advice is best first step.
Thanks guys.

On 11 of the 16 frames the leak is exactly like this. Same position, same intensity. 3 frames show no sign of the leak and 2 have very faint traces. Frame numers 1, 4 and 10 were not affected and frames 12 and 16 show slight traces sot it's not like only a part of the film was affected. It seems, well, a bit random when the effects don't show.

I agree I should study the film magazine first. It holds film now so I'll tape it up, finish that roll, inspect the magazine hold of the body and try another film magazine. I've been shooting with 645 models for years so the possibility of not locking the magazine into place is unlikely but I'm not ruling out anything now.

Last edited by Bas Stubert; 04-10-2021 at 12:58 PM.
04-12-2021, 02:46 AM   #8
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QuoteOriginally posted by Bas Stubert Quote
The other eleven shots all suffered from the same light leak as shown here. Now this puzzles me. I would have thought that all shots would have been affected. I used the 645N with the film magazine that was supplied with it. I am wondering what causes this. Is it the camera itself? The film back? If you've got an idea please drop me a line!
Based on what youʻve described, the leak would either be caused by a bad seal on the film back holder or an issue with the first or front shutter curtain.

The inconsistent frequency of the leak is usually because of a combination of the amount of ambient light and amount of time between shots.

Next step is process of elimination. Do a test roll. After loading the film, put an opaque tape to seal all four sides of the film back insert. Use the camera in full daylight for about as long as the rolls that showed problems.

If the problem goes away, then it is a seal problem with the film back insert. If it persists, then your front or first shutter curtain is not closing sometimes and is folded open and needs to be repaired or replaced (very expensive).

04-12-2021, 03:54 AM   #9
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QuoteOriginally posted by Alex645 Quote
Based on what youʻve described, the leak would either be caused by a bad seal on the film back holder or an issue with the first or front shutter curtain.

The inconsistent frequency of the leak is usually because of a combination of the amount of ambient light and amount of time between shots.

Next step is process of elimination. Do a test roll. After loading the film, put an opaque tape to seal all four sides of the film back insert. Use the camera in full daylight for about as long as the rolls that showed problems.

If the problem goes away, then it is a seal problem with the film back insert. If it persists, then your front or first shutter curtain is not closing sometimes and is folded open and needs to be repaired or replaced (very expensive).
Sound advice Alex, thanks! As you and the others have suggested my first step is finishing the roll that is now in the camera with the film compartment all taped up and take it from there.
04-16-2021, 04:43 AM   #10
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Good luck with this. You may be able to find another film back on ebay or at your local camera store, so you could try that as an alternative and see if it makes a difference.
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