Light Leak on M3 is driving me nuts.

Agiknee

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Ok, I bought this M3 recently. When I purchased it I did the light through the curtains trick in my dark bathroom several times with no signs of pin holes of light coming through.

The area surrounding the backdoor had been resealed fairly recently as that was the source of the light leak.

Previous owner assured me that it was light tight.

I sent the body off to Youxin for a CLA as the shutter timing was off compared to myMP. I finally got around to developing my one roll of b/w I shot through the cam and low and behold there’s a light leak.

I’m so frustrated. I can see it being the strap lug but also I know curtains tend to go. What kind of leak does this look like to you?

https://imgur.com/a/jix729d
 
Topside back door. It's supposed to have a little strip of black cotton inbetween the door and the rail. That's likely missing a bit, or the door is slightly warped
 
If you run a roll of color film through it you can determine if the leak is at the front or the back. From the front, or through the curtains the leak will be white, if it is from the back then it is exposed through the film base and will be reddish.
 
I'm always sceptical about film door sealing in M cameras. I had M3 ELC untouched from Midland and I can't find those sealings. They must be very tiny. No light leaks. Best camera ever made from those I have. I'm just not 50mm user.
 
Once, and I mean only once, I found a light leak by using foil and taping it with masking tape all around the door. It was frustrating because I removed sections of the tape at 5 frame intervals and it was the first removal. Therefore, the rest of the roll was ruined. You could try this if everything above fails.
 
Once, and I mean only once, I found a light leak by using foil and taping it with masking tape all around the door. It was frustrating because I removed sections of the tape at 5 frame intervals and it was the first removal. Therefore, the rest of the roll was ruined. You could try this if everything above fails.

I’m going to have to try this method. Youxin cannot guarantee that the CLA will cure the light leaks. I asked him to replace the seals again and hopefully that’s it. The last thing I wanna do is replace the curtains or straplugs.
 
Go into a nearly dark room and let your eyes adjust 5 minutes. now take off the back and bottom. Shine a pen light around the outside while you look at inside. Check around all openings. The leak is at the camera top. A very small keychain or pen light is necessary so as not to ruin hight vision.

If you can not find it, open shutter on B and replace back, look through front while shining the light around the back.

If all this fails, then tape all openings, use some cheap film and pull off tape and known intervals until the leak is uncovered.

Best to find the leak yourself because repair people will not want to do what is required. They will repair if you direct them.
 
If it is exposed into the sprocket area then it pretty much has to be from the back. As others have said, the primary suspect is the back door seal. These can be so frustrating to track down -- I had one with my M3 and it finally cured itself somehow...

I would also shoot another roll of film (different type) to rule out the film itself...

Rolfe
 
There is no seal material around the back door except at the top, three side have a "labyrinth" seal. Sometimes you find someone has stuffed something black into the labyrinth. The top side has a strip of shutter cloth glued under the hinge on the body side, continuing up under the top plate. If you remove the door you can see it better, and probably tell where it is leaking. I ran a strip of gaffer tape in that channel, after removing the original, and it fixed my leak.
 
Thank you all for info and suggestions. Really hoping in getting this Camera in running order. Going on a big trip and I’m going to be taking it along with my cron 50
 
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