. Sharpness From Corner to Corner The tried and well-proven optical design of this lens provides for a perfection of picture quality extending all the way to the extreme corners of the image field even at full aperture, as well as outstanding contrast throughout, at all apertures, even at close distances. Stopping down to f/2.8 or f/4 brings only a minimal increase in contrast. Distortion is extremely low and practically invisible. Its well-balanced design makes this ideal standard lens an outstanding choice in terms of all criteria, including image quality, speed, size, weight and price.