> I have heard remarks that a 200/2.8 prime will transmit more
> light than an 80-200/2.8 zoom. Is this true? I thought a
> 200/2.8 was a 200/2.8 whether it be a prime or part of a zoom.
> Thanks for any help.
I'm with you 2.8 is 2.8. Two different lenses, if calibrated properly,
should deliver the same amount of light at the film plane when set to 2.8.
No ifs, ands, or buts! Otherwise photography doesn't work with
interchangeable lenses.
Most zooms these days will change maximum aperture over their zoom range. It
is cheaper to build a lens this way. But some of the old Pentax A series
lenses held a constant aperture over their zoom range...A35-105/3.5 and
A28-135/4 come to mind.
Regards, Bob S.
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