Ivan Prenosil wrote, re effective lens aperture:
> It can't be (as people sometimes say on this list) as simple as
> lens diameter divided by focal length; otherwise my FA28-70/4
> could not be constant aperture zoom :-)
Hi ...
Like you, I don't believe it's as simple as diameter/focal length, and
somewhere i have the details of that. I've noticed, for example, that
my Leica lenses are often quite a bit smaller in diameter than the
same focal length/aperture combination in Pentax and other SLR lenses.
However, zooms can be a constant aperture. I have two Pentax zooms
w/constant aperture. There is a mechanical means by which the
aperture diameter is adjusted as one moves through the focal range.
This is apart from the aperture ring on the lens.
--
Shel Belinkoff
mailto:[EMAIL PROTECTED]
"Why should I use a meter? What if the darn thing broke on me
when I was out making a photograph? Then what would I do?"
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