I think the problem is that the mirror lock up only raises the mirror away
from the rest of the mechanism, rather than bypassing it, so the saving in
moving mass is less than you might expect. In raising the mirror it also
bypasses the air damper, which would increase the vibration from those bits
which still move.
My suspicion is that it was actually not really intended as a vibration
reduction measure, but was a hedge against not being able to make the
superwides sufficiently retrofocus to allow the mirror so be used. Of course
by the time the OM2 came along they had achieved it, so the mirror lock up
became dispensable and was duly dispensed with- irretrievably. They could
easily have designed the OM2 so that the OTF meter on-switch was activated
by a different component than the mirror itself, but they didn't.
This would explain why they didn't bother with it for the OM3.
The other reason for the MLU on OM1 is that this is the only way of getting
5FPS from the Motor drive.
The lack of a self - timer / aperture prefire / mirror raise on OM3 is
easier to explain.. It would only have been possible to do a ST using an OM1
self timer, i.e. a robotic shutter-button press, which would have brought
none of the advantages that the OM4 ST brings, only the consumer-oriented
firing delay. Not really a USP on a pro camera. The electronic interrupter
of the OM4 (which allows the entire mirror cycle to execute before allowing
the first-curtain release to trip) simply wouldn't fit into the mechanism of
an OM3. It needs a ruddy great electromagnet right about where OM3 needs a
timer stack. could have been re - engineered but OM3 was never intended to
be a volume seller.
Julian
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