how does A99 calc exposure with a manual lens?  Started Feb 16,
2013 | Discussions thread Contributing MemberPosts: 890Gear list
Re: how does A99 calc exposure with a manual lens? In reply to
William Porter, Feb 17, 2013  William Porter wrote:  My question
(by the way) was simply about how the live display works when
the camera doesn't control the lens aperture. I wasn't asking
about how the camera calculates exposure settings (it's NOT
calculating, I'm in M mode so I'm doing the calculating) nor
about what happens when I click the shutter (which I
understand).  And the answer is basically as simple as you could
hope for: there's a video feed with a known electronic shutter
time and known ISO. Measure the actual video frames periodically
against a desired metering algorithm, decide that the image is
too bright or dark, and adjust the ISO or shutter until it's
where you want it. Aperture isn't needed for the computation,
because everything happens off the sensor stream.   Promit's
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