Re: [Leica] Curtain problem or what? Need your help!

["Anthony Atkielski" <anthony@atkielski.com>]

From: Jacques Leonard designer <j.leonarddesigner@videotron.ca>
Sent: Tuesday, September 21, 1999 05:37
Subject: [Leica] Curtain problem or what? Need your help!


> This darker area does show the picture. It just looks as
> if this portion was under exposed. Which is probably
> impossible.

I agree.  The curtain is opaque and the image hitting it is well focused.  If it
were the curtain, there would be no exposition of the image at all in that area,
right?  (Unless there is a slot or something in the lower part of the curtain
that could cause partial exposure even if it were misaligned.)  It would have to
be either something opaque moving in front of the frame, or something
transparent but dark positioned in front of it.  I don't know the construction
of the camera well enough to speculate on what that might be, exactly.

The main mystery is partial exposure.  That can only be from something moving,
or from something that diminishes (but does not block) the transmission of
light.

> If it had been on the vertical side of my pictures, I would have assumed
> this to be a speed problem. Unfortunately it is at the top.

Which means it's really at the bottom, doesn't it?  Given that the image is
reversed on the film plane, of course.

One thing that comes to mind is that the film may not be seated correctly in the
guides.  If it were too low, the top might be chopped off.  However, like an
opaque curtain, this would eliminate exposure entirely in the affected area.
One might speculate on movement of the film, but there is nothing that would
move it, except when the shutter is advanced, and that would be horizontal
movement outside the period of exposure.

Maybe there is something protruding into the film gate.

The fact that it does not appear on an entire roll at one time works against the
hypothesis of improper film alignment.

Have you tried watching the shutter to see if there is any obvious misalignment?
Against a light background with the back open, and/or with a long exposure, you
should be able to see something, if the curtain is the problem.

> I suspect a curtain misalignment if this is possible.

That seems mostly likely.  It's the only part moving in front of the film, and I
don't think there are any semi-transparent parts that could otherwise be
responsible for partial exposure.

  -- Anthony