On Thursday, October 09, 2008 at 1:22,
Moose <olympus@xxxxxxxxxx>wrote:
| Johnny Johnson wrote:
| > At 03:39 PM 10/8/2008, usher99@xxxxxxx wrote:
| >
| >
| >> Found it remarkable that the review says the performance is
| >> diffraction limited at f/5.6 at 35mm. Can't say I've seen that
| >> stated for any FF lens at that FL.
| >>
| >
| > The Zeiss Contax lenses that so many people rave about also peak at
| > f4 to f5.6 - at least up through the 135/2.
| >
| I was also wondering about that statement in the review. I suspect a
| statement that performance started to fall off after f5.6 would be
| more appropriate - and accurate.
|
| The Tamron 90/2.8 in Pop Photo's test had an optimum aperture for
| macro of - wait for it - f2.8, although performance was great down to
| f22. My test of the later, Di version showed the same thing.
It's easy enough to check - calculate the diffraction limit using f/stop and
focal length and compare with test results.
These days, it's not unusual to see diffraction limits being reached on the
short focal lengths most digitals use.
Process lenses used in print shops and chip foundries are almost always
used at maximum aperture for maximum sharpness. Of course, they don't
have to worry about depth of field or chroma since they use a tiny portion
of the spectrum.
Lens tech vastly improved once computing got cheap and new transparent
materials became available.
tOM
-- Facilius enim per partes in cognitionem totius
adducimur -
-
tOM Trottier, +1 613 860-6633
469 Ancaster Ave, Ottawa, ON K2B 5B6 Canada
http://Information.Architecture.Abacurial.com
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