2 bad lens from B&H, what is the odd

Started Apr 21, 2011 | Discussions thread
Steve House
Regular MemberPosts: 143
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Re: Nikon strangeness (is not so strange for professional applications)
In reply to Leonard Migliore, Apr 24, 2011

Perhaps it's an anachoronism with most of today's cameras and TTL metering, but if one is using a hand-held light meter, the effective aperture is what one needs to use when setting exposure. Actual geometric aperture controls depth of focus while effective aperture controls light transmission, hence exposure. With standard lenses the geometric and effective apertures are essentially the same so it doesn't matter but as others have pointed out, that's not true of macro lenses. Since macro work is frequently static in-studio setups lit by strobes and metered using a separate incident reading flash meter, it would make sense for the camera body used to work in effective stops so as to require less mental gymnastics to convert meter readings into camera settings. It's the same reason professional-grade cine and video lenses are calibrated for T-stops instead of f/-stops.

Leonard Migliore wrote:

...> I'm actually more comfortable with Canon's disregard of the effective aperture. I know the effective aperture is different from what's set on the lens, but if it's wide open, I'd rather it said f/2.8. With TTL exposure, you don't really need to know the effective aperture for anything but it's good to know if you've stopped down your lens or not.

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Leonard Migliore

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