> An f-stop is simply the ratio between the focal length
> of the lens and the diameter of the aperture. Nothing
> more, nothing less.
I think this line should be:
An f-stop is simply the ratio between the principal focal length of the lens
and the principle diameter of the aperture, Nothing more, nothing less.
This because the diameter needed to get an certain f-stop depends also on
the place of the aperture blades in the beam. Where this place is, depends
totaly on the design of an lens, and in a zoom-lens this place, combined
with the optical-design determines what influence this has on the maximim
f-stop it can reach.
Drikus
P.s. don't forget, that what you see when looking through the glasses of the
lens, isn't the actual size of the blades, and that with a zoom-lens that
size can change, without actually changing in diameter.
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