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[OM] OM1 miror lockup vs. OM4 mirror prefire

Subject: [OM] OM1 miror lockup vs. OM4 mirror prefire
From: WKato@xxxxxxx
Date: Mon, 17 May 1999 22:40:03 EDT
I just had a thought while here at work (it's ok I think about work when I'm 
home) and that if the mirror prefire also shuts down the diaphragm then it 
might be less prone to causing vibrations than the OM-1 where only the mirror 
goes up but then the aperture is closed just before the shutter opens. The 
shutting down of the aperture diaphragm might introduce additional vibrations 
just before the shutter opens that the OM4 does not have, which would be the 
worst time for any mechanically introduced vibration to occur. (See prior 
speculations as to the reason for subpar results at slow shutter speeds.)

I checked some bodies and found the following with use of the self timer:

OM1 no aperture stopdown with mirror lockup, with or without mechanical 
self-timer
OM2n no aperture stopdown with mechanical self-timer
OMF, OM10, OM2s and OM4T all flip up the mirror and stop down the diaphragm 
right after self-timer initialization and activate the shutter some time 
later.
OM77 has no stop down or mirror prefire with self-timer.
OM3, alas, has no self-timer.

Now for the combustible gas and spark question:  Could the lowly OM10 take 
sharper photos between its slowest limit(??) and 1/30 than the OM1 with 
mirror lockup?

Warren



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