The APO-Summicron-M 90mm f/2 ASPH. from Leica is a fast short telephoto lens designed for M-mount rangefinder cameras. As an apochromatic lens, it features a pair of anomalous partial dispersion glass elements to virtually eliminate colour fringing and chromatic aberrations. One aspherical element and two high refractive index glass elements are also used to control spherical aberrations and distortion. A bright f/2 maximum aperture benefits working in dim lighting conditions while offering greater control over depth of field. The lens uses a manual focus design that permits working with subjects as close as 1 metre away with a maximum magnification ratio of 1:9. The physical design also incorporates a built-in extendable lens hood to shield the front element to reduce lens flare and ghosting.
