Hi all,
>From: james king <jking@xxxxxxxxxxxxxx>
>testing at f11+ can mean long exposure times.
I generally shoot at wide apertures, so the smaller aperture in my tests
should be f/5.6 or f/8, depending on lens speed.
>However I think the results from B&W will
>need printing or scanning for you to make comparisons. I did quite a few
>tests with velvia 100 which allows you to make comparisons with a light
>table and loupe...
Yes, but I definitely need a _good_ loupe -- I want to check the lens'
aberrations, not the loupe's! I have used a 50/1.8 as a "highly corrected
loupe", although doesn't seem to give much magnification.
>From: Ken Norton <ken@xxxxxxxxxxx>
>Lens testing I've done on B&W has been done with Ilford PanF and Delta 100
I was thinking about these films...
>processed in Ilfotec DD-X.
...and that's my usual developer, too. Would be a reasonable combination.
>You can also use Ilford FP4 film in DD-X.
Not a favourite of me... and seems difficult to scan :-(
>This thick-emulsion film has
>tremendous "migration" characteristics which give the lens tests a
>definitive yes/no interpretation of the line-pairs
(see my reply to Chuck a couple of paragraphs below)
>From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
>I don't understand shooting B&W
Well, I shoot B&W frequently, so it's a reasonable option.
>and B&W, high contrast test charts if
>you're ultimately going to be shooting color film and real world scenes.
In fact, I have little interest on doing an analytic, numerical resolution
test -- I'd prefer to compare _subjectively_ the sharpness and aberration
pattern of the lenses, with somewhat realistic (although normalized)
"subjects"
>You could probably save on film by first filtering the duds with the
>digital. If the lens doesn't cut it in the center it's unlikely to do
>much good in the corners.
A very good point, indeed. I think I'll do that, then re-check the best ones
with film.
>From: Ken Norton <ken@xxxxxxxxxxx>
>Shooting the test charts in color is really only beneficial if you want to
>see the color aberations.
However, sometimes I shoot colour, and I'd like to know how the lens renders
it -- e.g. does it yellow?
>the only current choices that I would consider for
>high-contrast tests is Ektachrome 64T, Kodachrome 64, or Fujichrome
>Astia 100F.
I use Astia 100F a lot. I'm now trying the Provia 400X.
>If color negative films would work, I'd use Kodak Portra 160NC or the
>newest
>Fuji 160S without hesitation
I may try it, probably would "scan" well... thru the camera ;-) I have used
Portra 400NC (and VC) in 120 format with great results.
>We shoot res charts instead of "real world scenes" for lens tests because
>of
>controlled lighting and repeatability.
That would matter more if I want to "archive" the results as a reference to
comparte future lenses against them... but I'm trying to select some lenses
from a bunch, in the future I could just retest the selected one against the
new competitor, in probably different conditions thant the earlier test, but
still valid for the current comparison.
Many thanks to all for your help and ideas!
Cheers,
--
Carlos J. Santisteban Salinas
IES Turaniana (Roquetas de Mar, Almeria)
<http://cjss.sytes.net/>
--
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