On Thursday, October 23, 2003, at 03:43 PM, Mark Dapoz wrote:
On all OM's the aperture stop-down mechanism is triggered by the upward
force of the mirror springs. Even on the OM-1 when the mirror is
locked
up the spring mechanism still operates so that the aperture is closed.
The
amount of force and movement is constant regardless of the lens and
aperture
used. The diaphragm mechanism in each lens will control the amount of
movement needed for the selected lens/aperture combination. When
mirror
pre-fire is used, all this mechanical action occurs well before the
shutter
opens. That's where the benefit of the pre-fire comes in. Simply
keeping
the mirror raised as in the OM-1 doesn't stop any of that vibration.
Now
electronically activated apertures don't have any of these mechanical
linkages
so there may be less benefit to aperture pre-fire.
I think that answers it, Mark. Thanks.
Winsor
Long Beach, California, USA
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