Black Spandrels

[thuggins]

My apologies for those who my take issue with this being posted in the color film forum. But the issue showed up on the film, and XP2 is color film - just one color.

In my ongoing effort to run a roll of film thru every camera, the process has now come up to the FTL's. I picked a body that I hadn't shot with before and verified that the meter was good and the shutter sounded right. When the film was developed, pretty much every frame is over exposed. This is not a meter problem, it was reading just as expected.

Some of the shots have a black (unexposed) area in the lower left hand corner, which would be the upper right as it went thru the camera. Note that these are processed in E-6 chemistry so they are positives and the black area is unexposed. I initially thought the aperture wasn't stopping down fully, which would account for a two to three stop over exposure. But I cannot imagine how these spandrels could be caused by an aperture issue. While they are similar to vignetting, they only occur in one corner and vary in size. They don't look like a vignette.

That only leaves the shutter as a possibility. But it fires on all speeds and seems good from a visual and aural check. I have one body that was CLA'd a few years back and I know is good. This weekend I'll mount the same lens on it and see what happens.

BTW, this was an 50f1.8 lens. The Zuiko FTL lenses have an aperture lock down feature, so I can also experiment with that. In the meantime, any ideas?

 

[bernard_L]

• A piece of light-baffling felt or foam dangling from the top of the mirror box? If true, this would occur equally at all shutter speeds.
  
• The shutter curtains not separating or closing in on the top side. If true, this should disappear at "slow" (1/30 and longer) shutter speeds, where 1st curtain fully opens before 2nd curtain moves.

Do you have evidence on your existing roll? If not can you perform experiments to test these hypotheses?

 

[MattKing]

Any chance that the lens mount is bent? It looks like vignetting to me.

 

[Rudeofus]

Not sure whether this camera can do this, but can you try a shot with the rear hatch open? This way you could observe what happens while you take the pic (with no film, of course).

 

[Theo Sulphate]

Here's a wild shot that I don't actually believe: it's the mirror rising. The angle of the shadow is caused by the mirror rising over time as the curtains travel.

The reason I don't quite believe it is because usually on SLRs the first curtain is triggered only when the mirror is fully up. However, I am unfamiliar with this camera.

 

[AgX]

Is this so? Or is there rather a preset lag, independant of what the mirror actually is doing?

 

[Theo Sulphate]

Is this so? Or is there rather a preset lag, independant of what the mirror actually is doing?

Well, on Pentax SLRs, the first curtain will not release unless the mirror is fully up. So, the mirror is not actually a trigger - it is a precondition. That is common with other SLRs.

The OP's Olympus FTL may be different; I do not know that camera.

 

[Kino]

Are you sure it's the camera and not something like a strap laying across the lens? The blocked area is very fuzzy, suggesting in front of the lens, not near the film plane.

 

[thuggins]

Are you sure it's the camera and not something like a strap laying across the lens? The blocked area is very fuzzy, suggesting in front of the lens, not near the film plane.

I appreciate the suggestions. While I have left the lens cap on rangefinders, I have never once had my thumb in front of the lens, leastways on an SLR. It seems unlikely to happen a half dozen times on one roll, especially the one roll that was also overexposed.

The suggestion about the mirror seems like the only possibility. But it is odd as both the shutter and the mirror look good and fire snappy. I've cycled it many times and it looks just as it should.

 

[Theo Sulphate]

Can you remember the shutter speeds you used? For the frames that don't have the problem, are they at a slower shutter speed than frames that do have the problem? On frames where the black area is largest, were those frames made at higher speeds? If these are true, that would suggest you are seeing the mirror.

 

[thuggins]

The issue is definitely with the body and not the lens. The shots taken with the other body (same lens) came out fine. I'm going with a slight interference from the mirror.

Now it's just a question of whether to have to first body CLA'd. It is in great shape and the meter reads right on, so it seem a shame not to having it working 100%