This lens rates highly on resolution tests. It is similar to it's more expensive brother, the Contax Planar 50mm f1.4. These shots were taken on my T2i with a cheap adapter. It fits the body tightly but the lens has a little play. This particular lens has significant fungus on the rear element and a sticky aperture, but like most quality lenses it still produces nice images. Focus is well dampened. Aperture jumps from f1.4 to f2 thru f16. There is no f1.7 setting. It is made well but not quite up to Zeiss standards and that is to be expected. Tack sharp. It's that simple. It is a tad soft at f1.4, but only at minimum focus distance. It is very sharp at f2 and razor sharp at f4. Contrast is excellent. Shadow detail is exceptional, just like its Planar siblings. Color rendition is excellent. Backlighting does not cause noticeable color shifts. Bokeh is smooth and bokeh fringing is low. In extreme lighting it will purple fringe at f1.4. This is consistent with most Planars. Black and white images are beautiful from this lens. Tonal range and detail is superb.