I have purchased a couple of used OM-1n's lately and have been checking
the shutter speed using a laser pointer (BJ's special), a photo
transistor (actually a simple transistor i cut the top off of) and a
scope. The transistor is hooked up to provide just enough gain I can
monitor the shutter cutting the beam with the rise and fall time. I
checked several camearas out and discovered that often the rear shutter
curtain typically travels faster than the first shutter curtain. I
did this by placing the beam near the beginning and near the end of the
shutter travel. On one camera, speed set to 1/1000, the starting
shutter speed was 1200uSec and the ending speed was 800uSec. None of
the cameras had uniform shutter speeds between the first and second
curtains. The worst had the equivalent of 1/1200 starting and 1/2500 at
the end. Another 1/800 starting and 1/560 ending.
Is there a way to adjust the shutter travel speed for better matching?
and also the shutter speed? My conclusion is that speeds 1/500 and
above on older OM-1n's could give non-uniform exposure across the film.
Wayne
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