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04-11-2009, 11:47 PM   #1
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Pentax D FA 100mm f/2.8 macro. An excellent performer...

I just did some test shots of this lens using a K20D. some observations:

In high contrast shots there is significant purple fringing wide open until about f/5.6
and the lens produces the sharpest images at around f/11. Taking several samples, the results were consistent, all were taken using a tripod and 2 second time. I have yet to determine if SR is the culprit at long exposures, greater than 4 seconds. I have been having mixed results with SR so far.

The samples are at the slower fstop range to illustrate the excellent sharpness of this lens when stopped down. I should also mention that it seems the hexagonal reflections within the bokeh are almost gone by f/16. I don't know the technical name for the reflections, but you can see that this lens has 8 aperture blades.

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Last edited by aweir; 04-11-2009 at 11:58 PM.
04-12-2009, 01:59 AM   #2
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Join Date: Oct 2006
Location: Melbourne, Australia
Posts: 11,794
This is a very contrasty lens especially above f4 onwards

I would refrain from using aperture above f11. Diffraction would kick in to soften the images with desaturated colours.

DFA 100mm macro gallery

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