On Sat, 21 Nov 1998 10:29:35 -0800, "vonohlen" wrote:

>Some lens are "sharper" at or close to their maximum aperture. You actually
>can get a degradation of quality shooting at f11. The most difficult thing
>that I am relearning is to shoot more with the lens at or near wide open. (I
>was trained on TLRs and Speed Graphics ;-)

Hmmm, I have checked a LOT of lenses (including many of Nikon's
best...), and the above has not been my experience... Virtually
all good lenses for the 35mm format peak at f5.6-f8 in the
center (but the corners may peak anywhere from around f5.6 to
minimum aperture, depending on lens type). I have seen only one
lens that peaked in sharpness at a wider stop (f4, with soft
corners until the lens was stopped further down). It is true that
in a good lens for 35mm, performance relative to peak sharpness
in the center is very slightly degraded by f11; somewhat more by
f16; enough more by f22 that that stop is best reserved for when
DOF considerations are more important than sharpness; and f32
is best avoided. (BTW, "sharpness" is a subjective thing, and is
a combination of resolution and contrast...) As you point out,
best sharpness with larger-format lenses occurs at smaller stops
(about fll for 120, maybe around f16 for good 4x5-format lenses).