Originally posted by Kunzite SLRGear tested them as well; the DA 50mm it's not bad, despite its aged design (I have the FA it's based on, by the way) but the DA* is a modern design - sharp from corner to corner, even wide open (on APS-C).
The DA* 55 (a wonderful lens I got the use of one afternoon) seems to be like every other fifty in the business, Kunzite - based on the same old fundamental Zeiss design, following a familiar bell curve as shown by Photozone's testing:
Whatever a fifty does wide open, it's better a couple of steps down.
As the reviewers noted:
"The DA* 55mm f/1.4 SDM shows the rather typical resolution curve of a standard lens. It is fairly soft (inc. contrast) at f/1.4 and f/2 although the center quality is quite fine here already. There's a substantial boost in quality at f/2.8 where the center reaches an excellent level and the borders and corners deliver very good quality. The peak resolution is reached between f/4-5.6 where it is basically excellent across the board. At f/8 diffraction effects start to lower the resolution potential again (as usual). The lens showed no significant amount of field curvature."
I don't doubt differences in colour rendering and contrast, though.