>From: Manoj Shrivastava <[EMAIL PROTECTED]>
>Subject: RE: EOS Manual Lens Mount
>
>AFAIR, once I did used an Russian manual lens on my 500N and I set the
>camera in Av mode set the an apurture on lens. In Av mode set same value in
>camera using Command dial and camera calculates the correct exposure
>automatically. though you have to focus manually.
>
Can somebody tell me if the following conjecture is correct?
The metering system has to know what the metering (also of course the
viewing)
aperture of the lens is, right? When you mount an EF lens, the lens tells
the camera
during viewing what the metering/viewing aperture is; viz., the lens'
maximum
aperture. The camera knows what aperture the lens should stop down to
during the
actual exposure; either by calculating it or by being forced by the user via
Av mode.
Now, when you use Av mode on a fully manual lens, where there is no
communication
of aperture (or anything else) betweeen camera and lens. Does the camera
take
note of this fact and then assume that the set Av value is the
viewing/metering
aperture? I don't see any other assumption the camera's designers could
make that
would allow any exposure automation (in ETTL mode) possible with a manual
aperture lens.
DGW
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