On 25 Jul 2002 11:37:26 GMT, pentax711@aol.comjunque (Bob Hickey) wrote:

>I don't know. I never shoot at wide apertures. The absolute sharpest lens I
>have is a Zeiss Planar 75, f 3.5. That one is beyomd belief at f 8, but falls
>apart badly at f 16 . So that supports your figures. Strangely, the Planar on
>the Hassy holds up much better at small aps. The Summacron 50 seems to be just
>as good anywhere, or at least I can't see any difference.
>Hickster

If a lens "falls apart badly at f 16" (especially if for
medium format) and another similar lens doesn't, this
indicates a defect (probably poor element centering),
since most good lenses are diffraction-limited at
small stops, and similar lenses should show similar
characteristics once they are diffraction-limited...
BTW, I owned several Rolleis with f3.5 Planars, and all
showed noticeable field curvature that made stopping
down beyond f8 generally necessary, and all were fine
at f16...