=======
Anyone care to comment about this? A long lens that
would degrade after F4 by diffraction?
=======
it means that this lens is so sharp that it is diffraction
limited at f/4. diffraction limits resolution and most
lenses get better corrected as they are stopped down
and diffraction gets worse as they are stopped down.
this means that as you stop down a lens, it gets
sharper until diffraction takes over. the sharper
the lens, the wider the aperture where this
crossover takes place. most lenses are not
sharp enough at f/4 to hit the diffraction-limit
at f/4, which corresponds to an aerial resolution
of 400-425 lp/mm. At f/11, the diffraction-limit
corresponds to about an aerial resolution of about
150 lp/mm. so it takes a really well corrected lens to
be diffraction-limited at f/4.
joseph
< 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 >
|