Then what do you suppose is the purpose of the pattern printed on the
shutter curtain? Of course it is to provide reflected light to the
meter. First thing is that the automatic metering in an OM is center
weighted. The meter sensor is fixed and is unable to follow the slit in
the shutter across the film plane. It continues to point at the center
of the frame no matter what the shutter does. Since few of us shoot at
1/60 second or slower with any frequency almost all metering is done
with the film partly covered. The camera is metering the first shutter
curtain for the most part. That is one reason why film base color is
not a huge problem and also why flash photography would be
unpredictable when changing films with different color bases. Since
there is no pattern on the second curtain, metering would be horribly
in error if it continued to monitor exposure by the time the second
curtain gets much beyond a small amount of the way into the frame. So
metering is complete as you say by the release of the second curtain.
Since metering has to be complete less 1/2000 second, the fastest speed
on the camera and the delay for releasing the second curtain,then off
the film metering is pretty much marketing hype except for flash
photography. If you think about it 1/60 or slower is full frame
exposed, 1/125 is half, 1/250 is quarter and all ready an insignificant
part of a center weighted metering pattern. It is really off the first
shutter curtain and a little piece of the film metering.
Winsor
Long Beach, California
USA
On Sep 26, 2004, at 1:34 PM, Carlos J. Santisteban Salinas wrote:
> But OTF metering doesn't take any previous reading into consideration:
> just
> starts integrating actual light level upon release of the first curtain
> and, when the proper illumination is reached, metering stops and the
> second
> curtain is released.
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