Bob Meyer wrote:
>
> Way back in the dim, dark history of photography, some
> vendors did mark T numbers on their lenses. But the
> trend never caught on in still photography, for
> reasons unknown. In the movie industry, by
> comparison, lenses are always marked with T-Numbers,
> because it's critical that the exposure on film not
> change as the director selects different focal length
> lenses within the middle of a shoot.
>
> Let me say it as simply as I can:
>
> F-Stop is NOT related to the actual or measured
> transmission characteristics of a lens. It's
> calculated by mathematical formula. Two lenses with
> the same focal length and f-stop can have markedly
> different measured transmission characteristics, due
> to things like vignetting, internal reflections,
> different coatings, etc.
>
>
Bob,
I'm a little bit confused.
How do they test the lenses then when they say that the actual f-number is
not equal with the claimed f-number of a lens? And are light-meters then
useless when they state an certain f-number/time combination, without taking
in account this transmission-number? Or is the influence to small to notice
on the exposure of a photo?
Drikus
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