No distortion, vignetting from f/1.9 values. Overall high contrast and good reproduction of very fine structures, becoming somewhat softer in the outer zones of the image field. Astigmatism and coma are very well corrected with large apertures. The optimum aperture is f/4, which gives excellent reproduction of very fine detail across most of the frame. Compared to the Summicron (III), this recalculation is superior in terms of the high micro-contrast, which gives the fine details the special brilliance and clarity, and the reproduction of rough edges the sharpness. The differences are small, but the trained eye will recognize them.