The APO-Summicron-SL 90mm f/2 ASPH. lens from Leica is a short telephoto prime designed for full-frame L-mount mirrorless cameras. Offering an ideal focal length for portraiture, it can also be used with APS-C models where it will provide a 135mm equivalent focal length. This useful focal length is combined with a bright f/2 maximum aperture to benefit working in low-light conditions and with selective focusing techniques for isolating subject matter. The lens features an apochromatic optical design that uses anomalous partial dispersion glass to suppress chromatic aberrations for increased colour accuracy and clarity, and one aspherical element to reduce spherical aberrations for improved sharpness.
Multi-layer coatings have also been applied to individual elements to limit surface reflections, flare and ghosting for increased contrast when working in strong lighting conditions. Complementing the optical design is a Dual Syncro Drive stepping motor for fast and quiet autofocus performance to suit both photo and video applications, with full-time manual focus override available for even more refined focusing control. A floating elements system and an internal focusing design maintains consistent imaging quality throughout the focusing range, from 2 to infinity. An AquaDura coating has also been applied to the exposed front and rear elements to protect against moisture, and weather seals have been incorporated in the lens design to benefit working in changeable shooting conditions.
