Curt,
Welcome to the list. I haven't a clue what the answer is, but there are
some pretty knowledgeable people here.
Tom
> I have a question about the tolerance spec on the length or depth of the
> aperture coupling pin that sticks out of the back of OM-mount lenses.
This
> is the pin that picks up the spring loaded tab at the left edge of the
> inside of the body mount and couples in the lens aperture setting, I
> believe. I have a lens (a Vivitar 80-200 f/4 zoom) that gives me problems
> occasionally in that proper metering sometimes does not occur, usually
> after I've carried the camera around with the lens mounted. After some
> patient fiddling, I noticed that once in awhile, by moving the aperture
> setting ring back and forth, I could induce the failure which was
proceeded
> by a sound like a spring-loaded part snapping to its stop. Sometimes this
> sound occurred as the lens was being seated, in which case it again failed
> to meter properly. Under inspection, I decided the sound I heard was that
> of the body mounted spring loaded indexing tab slipping pat the aperture
> pin on the back of the lens. Being ever more curious, I used a crude gauge
> to measure the depth of the body tab below the face of the mount (6.0 mm),
> and then measured the protrusion of the coupling pin relative to the lens
> mounting surface for four OM-mount lenses I have access to - a Zuiko 50mm
> f/1.4, a Zuiko 50mm f/3.5 Macro, a Tokina 35-105mm f/3.5-4.8 zoom (now a
> collection of random parts, except for the mount/pin), and the Vivitar
Zoom
> in question. The two Zuikos and the Tokina all came in at 7.0 to 7.1 mm,
> while the Vivitar measured out to about 6.2 mm... which, given the limited
> precision of my measurements, does not seem to be long enough for reliable
> positive engagement.
>
> Anyway, all this is speculation and deduction based on a few simple
> measurements..... Does anyone have actual spec data on how long the lens
> aperture index pin is supposed to be? And, for that matter, does it seems
> at all possible that the length can be adjusted (extended) without major
> surgery to the lens? Given the added mm in length of the Zuiko lenses, I
> have no reason to believe that it is the body (an OM-4T) that is out of
> spec -- but again, this could be a hopefully deduction on my part!
>
> I'm new to the list, so I hope this sort of question is appropriate and
> acceptable. I eagerly await your thoughts and information.
>
> Curt Hedman
>
>
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