On Tue, May 8, 2012, at 08:21 PM, Chuck Norcutt wrote:
> Thanks for the link. I have these instructions somewhere (since I have
> a bigIS adapter) but I have yet to use it let alone program it.
What's holding you up? Your Zuikos are crying for attention.
> I spent a little time with the instructions and have concluded there is
> no magic there. The part about shooting in AV mode really has nothing
> to do with AV per se. It's all about allowing the chip report maximum
> aperture of the lens vs shooting aperture to be recorded by the camera.
I see that you're right. As long as you can lock exposure in Av or
meter in M it looks like the effect is going to be the same.
> Now to Mode AV. What we think of as AV mode is not happening here.
> Mode AV with respect to this adapter is just a trigger to accept the
> exposure measurement in stopped down metering mode rather than the wide
> open metering of Modes A and B and subsequent exposure lock. What gets
> written to EXIF is whatever aperture has been set on the camera. This
> is no different from Modes A and B except that for Mode AV you are
> advised to set the maximum aperture of the lens on the camera body so
> that that value is written to the EXIF. Presumably just a means of
> identifying the lens.
Chuck, when you put the camera in Av mode, set the camera aperture to
2.8 (or whatever you have programmed into the adapter as Max aperture,
and then stop down, you can see the shutter speeds change in precise
proportion to the stop. For all intents and purposes, this is aperture
priority.
If I move the camera around and track different levels of light
intensity within a scene, shutter speeds change in the display in
response to the volume of light, just like an OM-2 in A mode.
> If there are exposure problems between a particular MF lens's
> characteristics and the camera body's metering system none of this will
> straighten that out. You will still need to understand the particular
> characteristics of each lens and apply appropriate exposure
> compensation. If your "AV mode" on the adapter is giving you perfect
> exposures just count yourself lucky that stop down metering is working
> well.
OK, I'll take lucky any day.
Here something kind of interesting. I did some shooting with the camera
set to Av mode and the camera aperture set to 2.8. I used the Zuiko
300/4.5. So there is 1.5 stops difference between max aperture of the
lens and what the adapter "thinks" should be there. Should my exposures
have been under- or over-exposed?
Joel W.
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