The Leica APO Summicron-M 1:2/50 mm ASPH. has exceptional correction abilities that enable all aberrations to be reduced to a minimum level. Its key features include excellent contrast rendition, all the way to the corners of the image, even with a fully open aperture. The use of a "floating element" ensures that this is retained, even for close-up shots.
Distortion is very low at a maximum of just 0.4 % (pin cushion), which is practically imperceptible. A total of eight lens elements are used to achieve this exceptional performance.
The aspherical surface of the first lens in the rear group helps to reduce spherical aberration and flatten the image field. While the optical construction in front of the aperture is a Gaussian type, the arrangement of the lens elements behind it is similar to that in the Summilux-M 1:1.4/35 mm ASPH. This group comprises a "floating element", which is moved independently of the rest of the construction during focusing.