This ultra telephoto zoom lens covers a standard range of focal lengths from 50mm to 500mm telephoto range. This lens is equipped with Sigma's unique HSM (Hyper Sonic Motor) technology for quiet and high speed AF, while allowing full-time manual focus override. Four SLD (Special Low Dispersion) glass elements provide excellent correction of color aberration throughout the entire zoom range. Additional super coating on each glass surface creates a superior color rendition, while minimizing flare and ghosting. The Sigma 50-500MM F/4-6.3 EX APO HSM optical design is optimized for DSLR cameras.