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Old September 28th 05, 09:49 PM
Tony Polson
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The prime may be slightly brighter than the zoom, something which may
be more important in the motion-picture industry
They use a term called the "t stop" of a lens and it is a measure of
the light loss through a lens.
The difference could be as little as a third or as great as (or greater
than) a 2 stop difference between what the f-stop is and the t-stop,
while the DoF will be the same and sharpnes is likely to be less with a
zoom than a prime.

I would very much like to hear which particular lenses for DSLRs or
35mm SLRs produce a 2 stop reduction in illumination from that
expected at any given aperture.

You needn't list all of them, merely give some examples. ;-)

In real life still photography I don't believe it would be noticable
(the difference in brightness), because of a variety of factors.
I personally would not lose any sleep over it.

You wouldn't lose any sleep over a *two stop* reduction in
illumination? Either you are a very sound sleeper, or that reduction
simply doesn't exist. Or possibly both.