awilder
Alan Wilder
Posted here: http://www.photo.net/photodb/folder?folder_id=723455 are some interesting results for fans of either lenses. Something revealed that's rarely mentioned was that published calculated MTF curves for both lenses apply only when measured at infinity but at closer distances things change for the worse, even a much as a few meters but more so for the ASPH. In this case, the contrast and resolution tests charts are at a repro ratio of 1:51 or a distance of 2.55 meters. Scenic test shots near infinity are slightly crisper across the frame with the 50 ASPH at f/2 and f/2.8, but by f/4 the difference is practically nil. At the closer distance of 2.55 meters, centrally, the ASPH is the clear winner at f/2 and f/2.8 as one would expect. However, off axis at f/2 or f/2.8, astigmatism rears it's ugly head and cuts it's microcontast (40 lp/mm), progressively blurring very fine detail as you move out, compared to the Summicron which does a better job in keeping astigmatism under control. To it's credit, the ASPH does appear to maintain a little higher level of contrast in most of the mid-field but at lower frequencies (10 or 20 lp/mm) thus giving the impression of good clarity. By f/4 and beyond (not shown) the two are very close with the ASPH slightly edging out the Summicron in the outer field in all but the extreme corner where it remains a bit soft through f/5.6. Compared to the pre-asph version which suffered much more from off axis aberration and never exceeded the Summicron in these zones especially when closer than infinity. As one gets closer still (<1 meter) the Summicron holds and advances it's lead over the ASPH as Erwin Puts also concedes in his report.
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