Interspersed reply:
----- Original Message -----
From: "Shel Belinkoff" <[EMAIL PROTECTED]>
To: "Pentax List" <[EMAIL PROTECTED]>
Sent: January 25, 2001 10:29 AM
Subject: Filter Test
> I've taken the plunge and ordered several Pentax SMC filters,
> and would like to compare them to B+W and Hoya filters
(because
> those are the ones I have). However, I don't really know much
> about testing procedures, so I'm asking the list for some
> suggestions.
Sure. I'm good at that. Sometimes I'm even lucid
>
> Here's what I'd like to do:
>
> First, shoot a few frames of slide film with one of Pentax's
> finest lenses, sans filter, and using a few different
apertures
> - wide open, a stop or two down, f/8.0 and f/11.0, and at the
> smallest aperture. Then I'd repeat the test, using the same
> apertures, with each filter.
Sounds like the way I would do it
>
> My first thought is of which lens to use. It's been said that
> longer lenses suffer most from image degradation when used
with
> a filter, so it would seem that a lens in the 100mm or greater
> focal length would be a better choice to see any degradation
> than, for example, a 50mm or wide angle lens. So, here are
the
> lens choices. Which do the "testing mavens" suggest as being
> the better lens for this experiment:
>
A100/2.8 macro
A*200/4.0 macro
They are the highest resolution lenses of the bunch you listed.
>
> I'm thinking that the faster lenses may be the better choice
as
> the difference between wide open and a mid aperture is
greater,
> and any qualitative differences between wide open and smaller
> apertures may be easier to see.
Whatever.
>
> A test for flare and image degradation by a light source just
> inside and just outside the frame seems like a good option.
> Since the sun could vary somewhat in its intensity if I
> couldn't shoot everything at about the same time, would an
> incandescent light source work as well, or should I try to get
> everything done at once using the sun as a light source?
Use an artificial point source to repeat flare tests. A small
flash for example. That way is most repeatable.
>
> What might you recommend as a test subject? Using something
> that doesn't move seems ideal, although a brick wall may not
> provide the sort of visible detail needed.
Download the USAF test target from Rob Studderts website
>
> Any other testing suggestions?
>
> Bill, would you be willing to examine the results under your
> microscope? I know you've got a pretty full plate with the
PUG,
> so let us know. Does anyone else have the ability to examine
> and photograph slides for this experiment?
I can do that for you. You have my address
>
> Is slide film the best choice for this? It seems to allow for
> fewer variables. Can someone make a case for color negative
> film?
Use T-Max 100. Self process it. That way, there are fewer
vairiables still, and ugly as the stuff is inpictorial use, it
is just about the sharpest stuff around.
William Robb
> --
> Shel Belinkoff
"The difference between a good photograph
and a great photograph is subtleties."
I wish I had said that
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