--- Don Feinberg <donf@cybernex.net> wrote:
> > > 1. How would an individual, without any formal technical
> > > training, actually test this with a particular lens?
>
>
> You can't do it "easily" -- not without some equipment.
>
> And, about the f-stop calculation ...
>
> Here's a table of whole and half f-stops....
Thanks Don (you too Andy!). I have a table that was in Kodak's
Encyclopedia of Photography of years ago that lists 1/3 stops,
carried out to 3 decimal places. I sometimes use this to
convince my students I really know what I am talking about (vain
hope!). Anyway, it's just a bunch of damn numbers.
I'm aware that there is an optimum range at which any lens is at
its sharpest, optically speaking. At wider apertures aberrations
become more apparent; at smaller ones diffraction rears its ugly
head. I think it's important for a photographer to be aware of
this though it may be difficult to determine exactly what that
range is in any given lens. Except perhaps photograph some test
charts, something I have never done in my life and probably
never will do.
As for the actual f/stop values of zoom lenses, it has no
relevance for me personally since I don't use zooms. I was just
wondering about it because most of my students do use zooms -
the variable maximum aperture variety. Perhaps my two favorite
lenses, a 35mm f/1.4 and an 85mm f/1.4, aren't really f/1.4.
That's ok. I never have any problem with exposure. I do quite a
bit of low-light work, often shooting at f/1.4, and I mostly use
reversal film. Anyway, thinking about these numbers too much
gives me a headache. Or maybe it's just a Saturday morning
hangover. Thanks again.
Richard
=====
Richard Martin specializes in Cityscape and Waterscape stock photography as well as Children's Portraiture. E-mail: marphoto@yahoo.com
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