In article <4klf30$9bv@dfw-ixnews3.ix.netcom.com>, rzuch@ix.netcom.co says...

>Has anyone done any experimentation on the Nikkor 105mm 2.8 Micro AF
>'D' to see what the optimum aperture is? I tend to use mine for
>extreme closeups so I shoot it at f32 to get the widest possible depth
>of field, but am I sacrificing any noticeable sharpness by using this
>f-stop?

YES! (Read what I said below, it still applies....;-)
BUT, in macro, sometimes DOF considerations override maximum resolution
considerations (a photo of a fly is pretty useless if it is entirely soft except for one of its very sharp eyes....;-). When shooting bugs,
I am often down around f32-45 (working aperture, with losses due to extension, converters, etc. taken into account), and still have good sharpness in the images (relatively speaking!). But if you are setting f32 on the 105mm macro lens, you are actually using nearer to f64 at life size (smaller at larger magnification) and the results are
probably not very sharp. We can accept a somewhat softer than optimum
image of a macro subject (so long as it is not downright SOFT) in
trade for greater DOF without offending the viewer to the same extent
that an equally (un)sharp landscape photo (for instance) might.

>In <4kjihi$nsu@newsstand.cit.cornell.edu> d_ruether@hotmail.com (Bob Neuman)
>writes:
>>Lens optical faults limit wide-aperture performance, but most
>>of them get reduced as the aperture is stopped down. But
>>diffraction limits lens performance ever more as the lens is
>>stopped down. The result is that most 35mm lenses improve in
>>sharpness until about f5.6-11, then decline, with f16 being
>>the last really good aperture, and f22 being acceptable.
>>The better lenses can perform reasonably well at wider apertures
>>(like f2-2.8), but many need f5.6 or so to look really sharp.
>>This varies somewhat with lens type. When in doubt, use f8.

Hope This Helps