Paul Callomon
Collections Manager
Malacology, Invertebrate Paleontology and General Invertebrates
Department of Malacology
Academy of Natural Sciences
1900 Parkway, Philadelphia PA 19103-1195, USA
Tel 215-405-5096
Fax 215-299-1170
Secretary, American Malacological Society
On the web at www.malacological.org
>>> aydin <[log in to unmask]> 11/28/08 7:58 PM >>>
I would think that a macro lens closed down to f45 would create a lot of
diffraction effects.

No; the image is remarkably clear. The only optical issue I can detect is a certain reduction in sharpness at f45 due to the extremely small aperture (the "circle of resolution" effect), but this is made up for in part by the greater depth of field.
The best way to get good color pictures of microscopic things is to use an auto-montage machine. This is a microscope with a stepping focus attachment that takes a series of digital images while advancing the point of focus from the top to the bottom of the object; these images are then synthesized using computer software that discards the out-of-focus pixels and stacks the remaining image slices onto each other. The results are spectacular, but this is not a cheap machine and each image takes quite a long time to prepare. For point-and-shoot work, macro lenses like the 120 mm Macro-Nikkor or any of the Medi-Nikkors still do a good job. For information on the Mk2 and current Medi-Nikkors, see
http://www.mir.com.my/rb/photography/companies/nikon/nikkoresources/special/120medical.htm
The Mk1 can be seen at
http://commons.wikimedia.org/wiki/Image:Medical-nikkor.jpg
They occasionally pop up on eBay, and a working one for less than $300 represents a bargain in my opinion.

PC.

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