>My reference is an article entitled "Really Right Stuff for Photography
>Afield". I am uncertain of the original author, my copy is froma person
>named Dave Swager. Anyways, following the discussion on lens resolution in
>relation to aperture, the article states:
>
>"However, film resolution has also been shown to vary appreciably with
>aperture, and the resolving power is always highest when the light source
>area is minimized, to retard dispersion. This presents a troublesome
>dichotomy: Best lens resolution is achieved when shooting wide open, but the
>best film resolution is a f/22 (or smaller)! Obviously, compromise is the
>answer, and that is probably why most of the published ("on film") lens test
>for top quality glass indicate that f/8 is optimum, with f/5.6 and f/11 not
>far behind. So-what you learned about "optimum aperture" wasn't all
>wrong-but blame was certainly misplaced."
>
>The balance of the article takes an academic turn and deals with some of the
>math behind these assertions. I will be happy to provide hardcopy of the
>article to the interested reader.
>
>expressionless,
>John P
>______________________________________
>
>
>Joseph Albert <jalbert@xxxxxxx> asked
>>
>>I've never heard that film resolution varies with lens aperture, and it
>>is rather counter-intuitive-- might you be able to explain why this
>>would be?
>
I have to admit that this new to me. However, it does seem logical to me
that the optical conditions, such as the size of a physically larger
aperture, that would degrade an image on film would also act on the image
being observed with a microscope, the so called aerial image. It does not
make sense to me that you would have a wonderful high res aerial image and
a low res image on the film. There is no inherent advantage of of the
retina over film in resolving images that I am aware of. That is what one
is talking about when replacing the film at the image plane with a
microscope and an eye. It does seem to me that it is more likely that
aberrations that affect the image at large apertures will reduce resolution
whether the image is recorded on film or observed with a microscope. When
someone talks about the limits of one system, such as the diffraction of
the aperture, frequently it is done with the assumption that all other
systems are perfect - perfect lens, perfect glass, perfect coating, perfect
calculations, and manufacturing. All for the purpose of perfect
understanding? ;-)
Winsor
Winsor Crosby
Long Beach, California
mailto:wincros@xxxxxxxxxxx
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|