IMO aperture induced vibrations are much like that of
the mirror. Just before the shutter opens, the camera
continues to stop down the aperture as far as it will go.
When it reaches a physical barrier whose position is set
by that of the the aperture ring, it "collides", coming
to a stop causing vibrations. I am not sure if its
magnitude is as serious as that of the mirror's, but
can still make a measurable difference as evidenced
in Gary Reese's tests.
-Tim
I don't believe there is a hard stop in the aperture setting mechanism
relating to the aperture ring (can't feel or see evidence of one when
stopping down manually). If there is, this would generate an axial vibration
in the lens, which shouldn't (?) be visible. There is a hard stop at the end
of the travel of one of the actuating levers however. Which comes first -
the stop on the lens or the stop in the body? judging by the remaining
travel on the lens lever with the blades fully closed, I would guess that
it's the body lever which hits the stop. Maybe Olympus could have damped
this more effectively, since the excess travel on the lens lever makes the
exact position of the body - lever - stop non - critical. This would also be
the prime suspect as it would cause a vertical vibration, which would be
visible.
Julian
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