(From Sigma lens literature) The Sigma 50mm F1.4 DG HSM Art has been reengineered and redesigned to set a new standard of performance in the Art line. A staple focal length, the new Sigma 50mm F1.4 Art is a pro level performer for full-frame DSLRs great for many different types of photography including portraits, landscapes, studio work and still-life. It has been updated to include SLD glass and optimized for rich peripheral brightness with improved large aperture performance by positioning wide elements into the front groups.
Other updates include an optimized autofocus algorithm for smoother focusing and a floating focusing system to reduce lens movement while focusing. Under the Global Vision line, it features a new matte finish, improved AF on/off switch and guarantees every lens is tested with Sigma's proprietary modulation transfer function (MTF) "A1" measuring system before being shipped. Now with 13 elements in 8 groups compared to the previous 8 elements in 6 groups, it also has improved close focusing at 15.7 inches and a maximum magnification ratio of 1:5.6.
The lens incorporates Sigma's Hyper Sonic Motor (HSM) system to produce quiet, high-speed auto focus. In addition, it includes Super Multi-Layer Coating to reduce flare and ghosting, and to ensure high-quality images throughout the entire zoom range. The 50mm F1.4 DG HSM lens is also compatible with Sigma's USB dock and the company's Mount Conversion Service.
