I was looking at Norman Koren's site,
http://www.normankoren.com/Tutorials/MTF7.html
in which he discusses digital v. film argument in some detail. (He
says digital has just won the battle with the latest round of
cameras) One thing that he points out which I had not considered
before is diffractive resolution loss with physically small sensors,
and lenses. We are used to the beginning of softening due to
diffraction with 35mm lenses at F16. Since diffraction is a
characteristic of the physical size of the aperture which becomes
smaller for the same F stop in smaller formats it will be greatly
increased in the small digicams. Expect softening in the new Oly to
start about F8?
Small sensors run into problems with lens diffraction, which limits
image resolution at small apertures-- starting around f/16 for the
35mm format (43.3 mm diagonal). At large apertures-- f/4 and above--
resolution is limited by aberrations. There is a resolution "sweet
spot" between the two limits, typically between f/5.6 and f/11 for
good 35mm lenses. The aperture at which a lens becomed
diffraction-limited is proportional to the format size: a 22 mm
diagonal sensor becomes diffraction-limited at f/8 and an 11 mm
diagonal sensor becomes diffraction-limited at f/4-- the same
aperture where it becomes aberration-limited. There is no "sweet
spot;" the total image resolution at optimum aperture is
considerably less than for larger formats. Of course cameras with
small sensors can be made very compact, which is attractive to
consumers.
--
Winsor Crosby
Long Beach, California
< 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 >
|