William Sommerwerck wrote:
>
>A bit more thought shows that there is another way to take full-aperture
meter
>readings. Instead of placing the aperture-position pin at a particular
f-stop,
>you can reposition it to compensate for variations in the lenses' maximum
>apertures. Minolta was probably the first company to do this, and it's the
>system OM cameras use.
I've just looked at my fastest and slowest Zuikos, a 50/1.4 and an
85-250/5. When they are set to maximum aperture, the pin is in *exactly*
the same place (relative to the red marker dot) on both lenses. So how is
this telling the camera what the lens's maximum aperture is? All the meter
needs to know is the *relative* aperture from maximum so it can apply a
correction factor based on the difference (if any) bewteen the aperture at
metering time and the aperture at exposure time. Nothing more or less.
The only reason to transmit maximum aperture information to the camera body
is for viewfinder information purposes, and the OM series don't display
aperture information in the viewfinder. As a result, they don't need to
know the lens's maximum aperture.
>
>I was surprised at the generally incorrect responses to the original
question,
>the most-common being that, since the meter reads through the lens,
>compensation is automatic. Well, it ain't.
Why not?
>"Think, people, think!" -- Lex Luthor
Look at your lenses, William :-)
Richard
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Hemel Hempstead,
England
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