on 11/15/01 2:10 PM, ll.clark@xxxxxxxxxxx at ll.clark@xxxxxxxxxxx wrote:
> Almost any professional photographer will tell you that the only
> reliable way to test lenses for your own use is to test them yourself.
> This is an annoying, time-consuming and demanding task. Virtually all
> consumers lack the patience to do it. Since there is no consumer demand
> for such data, they are not
> produced.
>
> QED.
I was thinking about this recently, and - without getting too involved -
what is a good way to test a lens? I'd welcome comments on my proposed
procedure:
I thought maybe I'd tack an opened flat newspaper page up on the wall (in
sunlight) and set up the camera on a tripod. Vary the distance i.e. close
(minimum focus) medium (6-8 feet?) and distant (15-20 ft?) and maybe a
couple shots further out. Or should I use some multiple of the lens' focal
length? Then shoot (slide film) a range of exposures varying aperture and
shutter speed, being careful to minimize camera vibration on each shot.
Project the slides big, focus the projector carefully, and then go up and
look close at the projected image. Being black and white (approximately) it
should show some contrast information as well as sharpness.
I know there are test charts you can buy, but I'm not getting that obsessive
or scientific about it. I'm just curious enough to invest a roll of film and
developing to see what I can see.
I recently got a Vivitar 90/2.5 macro lens, and I want to see if the lens'
reputation is justified...
--
Jim Brokaw
OM-1's, -2's, -4's, (no -3's yet) and no OM-oney...
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