At 09:06 PM 5/2/99 +0200, Richard wrote in part:
>
>With an OM-1, the 200mm showed horrible vibrations, using the mirror prefire
>helped not much.
>
I assume you mean mirror lockup with OM-1, as timer (i.e., "prefire"
initiator) doesn't lock up mirror prior to shutter firing.
>Much better was the OM-4, less vibration then the OM-1, the difference to
an OM-1
>with mirror fliped up was hardly noticeable.
>Used with selftimer, the OM-4 was way ahead of the OM-1. Prefireing of
mirror
>and aperture seems the way to go.
>
>To verifiy this I prefired the aperture of an OM-1 with flipped up mirror
(taped
>the DOF button down).
In other words, you defeated the "auto" feature of the lens. Very clever!
>This had an very noticeable effect of reduced vibrations (practicaly as
good as
>an OM-4 with selftimer). Prefireing of the aperture alone had an much
bigger effect
>on reducing the vibration than a simple mirror prefire.
>
>With other lenses (180mm and 100mm) I was not able to find such big
differences
>between the OM-1 and OM-4.
>
>It seems that the problem lies in a combination of the way the aperture is
actuated
>and the long lens barrel, camera tripod thread combination, which results
in a long
>lever, moving like a spring.
>
Regards
Richard
p.s did someone test the OM-2SP vibrations wise? I guess the slower
aperture/ mirror
movement might be a benefit in this regards.
Richard, all of my "tests" have been with OM-2S, and I've gotten bad and
good results, depending on what precautions I take.
But thanks for this splendid detective work. Very clever experimenting. I
hadn't thought about the aperture as source of movement. My recent tests
with the 200/f4 and flash (with good, sharp results) had tended to confirm
that some sort of movement was being induced somewhere.
Bad news is that "pre-firing" the aperture isn't really a practicable fix.
I have found that the Bogen Telephoto Lens Support 3420 helps me get better
results with the 200/f4, undoubtedly for the reasons you have uncovered.
Joel
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