The Sigma 28mm F1.4 Art DG HSM Lens is characterized by its high optical clarity and smooth autofocus performance. This prime lens is compatible with Sigma SA-mount cameras. The lens design of 17 elements in 12 groups includes two FLD three SLD and three aspherical optics to minimize chromatic and spherical inconsistencies. A super multi-layer coating is applied to enhance image saturation. There is a protective coat on the front element which resists moisture and dust. The hypersonic AF system ensures silent and fast autofocus. With the manual override you can accurately focus on an object. The rounded 9-blade diaphragm offers circular bokeh quality. This Sigma has a weather-resistant construction to support outdoor shooting in challenging weather. You may plug the lens to an optional Sigma USB Dock to fine-tune the focus settings and update its firmware.