There are two levers on the back of the Zuiko (or other full-aperture
metering lens). One stops the lens down, the other tells the meter what
aperture the lens is set to. You can see this on the back of the Zuiko; when
the aperture ring is turned one lever will move in sync with the aperture
ring. This is relaying information to the meter, telling it what the
aperture will be when the lens stops down for the exposure.
Maybe too much semantics, but that last statement is IMHO not
entirely correct. If the lever did tell the meter what the aperture
was going to be during exposure, the meter (or your OM) could then
also tell you. One reason this information is not available in the
viewfinder, is that the lever is talking to the meter only about the
difference in aperture between fully open and stopped down.
Correct me if I'm wrong.
Ton
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