Leica M4 Shutter capping

[Joe878]

The horizontal striping on this one still makes me think the issue is with the actual edge of the shutter, as I mentioned in post #8 in this thread. It's a lot less extreme than some examples I've seen, but it's the only thing I can think of that would create those horizontal lines. And, again, it makes sense that it only shows up on 1/1000 (a jagged/ragged edge to one curtain effectively reduces the gap between them in certain sections; when the gap between the shutter curtains is already that narrow, it's a much larger reduction in effective exposure time in that area than it would be at even 1/500), and it also makes sense that some technicians wouldn't spot it (the guy I rely on to fix my old screwmounts had never seen anything like it; it just doesn't seem like it's a particularly widely-known problem).

I'm seeing absolutely nothing that would constitute "capping" (i.e. uneven exposure with one end of the frame darker than the other), though.

Funny enough when I was scanning the photos this morning, I pulled out the camera and looked at the curtain and it has indents where these marks show up. I do believe the camera had a shutter capping issue at one time. However now it may be fixed and this issue still persists.

These two photos were taken within minutes of each other although I’m not sure of the shutter speed. It was also developed at a different lab.Photos

 

[GMOG]

The horizontal striping on this one still makes me think the issue is with the actual edge of the shutter, as I mentioned in post #8 in this thread. It's a lot less extreme than some examples I've seen, but it's the only thing I can think of that would create those horizontal lines. And, again, it makes sense that it only shows up on 1/1000 (a jagged/ragged edge to one curtain effectively reduces the gap between them in certain sections; when the gap between the shutter curtains is already that narrow, it's a much larger reduction in effective exposure time in that area than it would be at even 1/500), and it also makes sense that some technicians wouldn't spot it (the guy I rely on to fix my old screwmounts had never seen anything like it; it just doesn't seem like it's a particularly widely-known problem).

Coldkennels, I have seen what you describe in thread mount bodies. You're absolutely correct about uneven edges being an issue when the slit is too narrow and/or the edges are particularly jagged. However, M cameras don't have exposed curtain material at the edges. They are completely covered by metal, so the edges are hard lines without any texture.

 

[Joe878]

The shutter on my camera has clear indents where the the particular wide dark mark appears in the upper right hand corner. I’ll post a photo later.

 

[Godfrey]

I agree with @Coldkennels ... I don't see much in these frames indicative of shutter capping.

It must be said: The three frames presented are a not a great test case for exhibiting shutter capping. You're using a very wide angle lens, which naturally has a good deal of corner/edge light fall off, for two of these samples. The best way to make test exposures for shutter capping:

- Use an evenly lit light box or clear blue sky at noonish as your test subject.

- Use a normal to medium telephoto lens, set to infinity focus, and stopped down between f/5.6 to f/16 to maximize evenness of illumination across the FoV.

- It's best to make exposures at every shutter setting, so with a film camera and fixed ISO, you have to have ND filters to correct exposures outside of the range of f/5.6 to f/16. (With a digital camera, you can adjust ISO to compensate for exposure and leave the aperture setting fixed.

- It is best to fix the camera to a stand or tripod in order to prevent camera motions from influencing the exposure across the field of view.

What you're looking for with a horizontally running focal plane shutter (eg: Leica M4) is the evenness of density on the captured, processed exposures in the horizontal direction across the film plane. If the density is brighter on one end than the other, or the density is barred in this direction, that indicates either capping or simply the shutter curtains' brake is getting worn and allowing the curtains to run unevenly.

Example: My M4-2 shutter exhibits unmeasurable variation from one end to the other at exposure times from 1 to 1/250 sec, about 0.1EV variation @ 1/500 sec, and about 0.3EV variation at 1/1000 sec when tested this way. The exposures are otherwise even, without barring. That says to me that the curtain brake is getting worn, and is now out of spec at the the two shortest exposure. I first measured this shutter about 11 years ago, and deferred the needed shutter overhaul since these variations are small and I don't use 1/500-1/1000 sec very often. I measured it again recently to see how much it has changed in the meanwhile and the results are virtually identical to what I measured in 2013 ... but it still does need a shutter overhaul.

Of course, a shutter testing device will give the same data without the need to expose a roll of film and process it, as well as more accuracy. 😉

The horizontal striping (as @Coldkennels suggests) is the more significant issue from what I see in the photos you've presented. I would get that camera to DAG for him to test, evaluate, and repair.

G

 

[Coldkennels]

Coldkennels, I have seen what you describe in thread mount bodies. You're absolutely correct about uneven edges being an issue when the slit is too narrow and/or the edges are particularly jagged. However, M cameras don't have exposed curtain material at the edges. They are completely covered by metal, so the edges are hard lines without any texture.

The metal lath could still be uneven - I've seen dents, corrosion, and general wear-and-tear that all results in a somewhat jagged edge. The smaller the gap between the two shutter curtains, the smaller the imperfection needs to be to cause issues.

 

[GMOG]

The metal lath could still be uneven - I've seen dents, corrosion, and general wear-and-tear that all results in a somewhat jagged edge. The smaller the gap between the two shutter curtains, the smaller the imperfection needs to be to cause issues.

I see your point. And yes, these issues create problems at the fastest speeds when the slit is relatively small.

Cheers!

 

[Joe878]

I just wanted to say thanks to everyone who replied and shared their advice.