Odd light leak on M4-P - can you help?

[Andrew3511]

I've been getting a light leak (or what looks like one) on my M4-P for a few months now and it seems to be getting worse. I have scanned a couple of strips of film that show it and I would be grateful for any advice. Before I get the standard one (send the camera for a CLA) I would just say I have got that on the to do list for when funds allow, but just at the moment and for the next few months they don't. I'm quite happy to walk around with black tape on the camera till I can afford that, but I need to know where to put the tape!

A couple of things I have thought about the leak -

The camera has been scuffed badly at the back by one of the little lugs that attach the rear flap, but the attachment itself seems secure and I can't see any evidence of a gap (it's the corner closest to the take-up spool).

The fogging on the film is clearly NOT coming from the lens side of the gate during exposure as it spreads into the edge of the film itself.

And now the most puzzling bit - if you look at the pattern on the edge of the film you can quite clearly see that there is fogging that bears the imprint of another set of sprocket holes. This implies that this happens when the film is actually wound up round the take up spool, and the pattern suggests very strongly to me that the light leak comes from the top edge of the film (bottom edge of image) downwards into the image forming area. Yet I can't see any evidence of anything up at the top of the chamber which even can leak, let alone is.

Any assistance gratefully received - will be out most of today though so I won't be able to do much feedback till this evening (UK time)

Andrew

 

[AusDLK]

From the description it sounds like there may be a leak coming through the back door on the film spool side. If you seal that with some tape does that help?

 

[stevence]

My M4-P exhibits the same light leaks. I'm quite positive it has something to do with the backdoor as well, since it's got a bump there. The problem gets worse in summer. My repairman told me this was nearly impossible, that you to run over it with a bus for this to happen, but apparently the problem is not so uncommon.

 

[Andrew3511]

I will probably (unless anyone has any better ideas) tape over the flap at the top hinge and see if that sorts it out. Stevence what else did your repair man think could be doing it if not the back flap/door?

 

[stevence]

He believed it was a processing mistake: I haven't dealt with him since. Internet searches reveal all kinds of problems: another possibility was the shutter seeping light and/or the curtains not closing at the same speed, but the backdoor seems the most plausible solution. I will try and tape mine to see if it goes away as well.

 

[Andrew3511]

It's not anything to do with the shutter, it's obvious that the light is getting onto the film from the edge and there is no change at the edge of the image forming area so the leak can't be from the lens side of the shutter box. I think it must be the door - we shall see. I'll apply tape and run another roll through soon and report back. It can't be my processing. It has happened with colour negatives and slides professionally processed and with B+W I have done. There is no problem with the M2 I have. I would probably have been onto it quicker but I tend to put the colour film in the M4-P and B+W in the M2 and I initially just thought it was a bit of flare. You don't really look at your negs critically unless you do them yourself, then you see it's not just the image area so there has to be something else going on.

 

[FPjohn]

M4

M4

Hello:

Is this a Canadian M4-P? My Midland M4 has always had a slight leak seen along the bottom of frames, detectable only on fast film, which has never intruded into the frame. I assume it is the fit between the bottom plate and the body.

yours
Frank

 

[stevence]

Mine is at the bottom as well, which means the light leak should be located at the upper part of the camera, since film is turned upside down in the camera.

 

[FPjohn]

Assume

Assume

Hello:

I do not assume that light can go around two right angles:just that the fit permits movement. Do you feel any play in the back? I've not but overall a M3 and M6 Wetzlar feel tighter.

yours
Frank

 

[ChrisN]

Hello:

Is this a Canadian M4-P? My Midland M4 has always had a slight leak seen along the bottom of frames, detectable only on fast film, which has never intruded into the frame. I assume it is the fit between the bottom plate and the body.

yours
Frank

Hi Frank - yours might be the "under the shutter curtain" leak (depending what you mean by "bottom of frame" - see http://www.rangefinderforum.com/forums/showthread.php?t=16364&highlight=leak

 

[FPjohn]

Outside

Outside

Hello:

Thanks for the link, the density occurs outside the frame and is not a "biggy"-I lose no sleep.

yours
Frank

 

[Andrew3511]

It's a Canadian M4-P, an early one, at work now, can't give you a serial number but was from 1981 IIRC. I can't really convince myself that the door is actually loose, but comparing with the M2 the fit is definitely not so good.