Bobonli
Established
I'm not sure whether foam should be there or not. It seems to me if there was a light leak it would be constant and appear in every frame. But it's not.
No M door I've ever seen has that foam.
Just to be clear, "foam" is my word. I don't know what it is. It could be a thin, old strip of rubber.
There should be none there. Just metal door, no rubber or foam. At least my M3, M2, M4, M6 and MP didn't have any.
The leak could happen only when strong light is trying to get inside of the camera thus not consistant leak on all frames. Would you wanna try removing the foam/rubber thing?
Shining light into back and front didn't reveal anything to my untrained eye.
Could that little bit of "foam" or whatever it is be the culprit?
Looks to me like some weird lens flare, not a light leak. The best way to find a light leak would be to load a roll of fast film and hit the camera body from all angles with a powerful flash. Do that for a few frames.
I say lens flare because in your low light shot with the blue spot, there appears to be no bright light source aside from the one in the frame. This is what is causing all your issues, but a shutter light leak would present in the exact same place. The one instance I can think of the shutter having a light leak which would cause this is if the metal leading or trailing edge of either curtain were wrinkled slightly. Still, the low light shot presents a very prevalent flare.
The other issue could be your processing service. The leader puller may be deforming the cassette just enough to allow a light leak in. After that, there may be internal light leaks in the processor itself if any one of the several baffles is missing.
I'd say do some more testing before sending your camera out to get serviced when the issue may be coming from a decentered or separated lens element, flocking missing inside the lens barrel or your processing service botching it up.
Phil Forrest
That's not too encouraging! I have my very first serious camera, a Nikon Fm from 1984 and it's be flawless it's entire life. So this is a bit of a shocker.
Oddly enough, the Leica M6TTL I bought out of "spite" has turned out perfect: not one single problem ever since it came to my hands.
Go figure...
Shocking! As the guru explained, "things wear out after 20 years, don't take it personally."
Update. Ran a roll through over the weekend and took it to another lab hoping the problem occurred outside the camera. No such luck. That "smudge" is in about 45% of the shots...