At 01:13 AM 9/16/99 -0400, you wrote:
>My OM4 has started intermittently (~1%) underexposing parts of the
>frame. It seems as if the leading curtain of the shutter is hanging up
>or something.
Tom, if it is the leading part of the frame and it occurrs at high
speeds, the shutters are being released at the same time with no gap,
and the curtains spread apart as they travel. This does not seem as
likely as the more typical reverse case, where the 2nd shutter catches
up with the first shutter at the end of the frame - which will cause a
uniform change in exposure across the film. If it is 1st curtain bounce
at the end of the frame, there is usually a dark band on one side. If
it occurrs mostly at 1000-2000 speeds, then a simple shutter adjustment
can fix the problem. I find that 1 or two clicks on the shutter
adjustments is necessary at least once a year or more to keep 1/2000
working correctly. I also try to avoid the highest speed for this
reason. And if 1/2000 shutter speed has a lot of variation, then a CLA
is called for and off to John the OM goes.
Wayne
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