"I also don't know why you wouldn't want to close the shutter when
proper flash exposure has been reached. What's the alternative? You
can't start closing before the flash is quenched, and why would you
leave it open longer?"
Actually, you _wouldn't_ leave it open longer. Rather, you would cut it
off at 1/60 (or the fastest flash sync speed).
If the quench signal from the camera is also used to close the second
curtain, and there isn't enough light for full flash exposure, the
shutter will remain open, continuing to record ambient light.
This probably _isn't_ what you wanted to do -- you mounted the flash and
set it to auto exposure because you wanted the _flash_ to expose the
picture -- you weren't trying to combine flash and ambient light. So we
want to be certain that the shutter closes
There is no "right" and "wrong" in this matter, though. You might very
well want the flash to correctly expose a foreground subject, while the
camera provides ambient exposure for the background. Many P&S cameras
(including the IS-10 and -20) provide this feature, but it works only
because the camera has autofocus that can determine the distance to the
main subject. The flash can then provide the correct exposure for that
subject, while the shutter stays open long enough to record the
background.
This won't work very well on an OM camera. The camera knows nothing
about the distance to the subject, so it cannot provide correct exposure
in a situation where a subject is in front of a dark background. To put
it another way, the automatic flash on the OMs assumes that the flash
will more or less evenly illuminate the entire scene. Under such
conditions, it makes more sense to force the shutter closed after 1/60,
rather than leaving it open to catch more ambient light.
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