Sigma 500mm f/4.5 EX DG APO HSM Autofocus Lens for Canon EOS Type: Telephoto Lens Focus Type: Auto Focus Diameter: 46mm (drop-in type) Compatibility: For Canon Features: Fast maximum aperture F4.5 telephoto lens optimized for digital SLR cameras. New coating reduces Ghost and Flare It is equipped with ELD (Extra Low Dispersion) glass elements It also features a rotatable drop-in filter HSM (Hyper Sonic Motor for Sigma, Canon and Nikon mount lenses) Inner Focus Accepts both 1.4X and 2X APO EX Tele-Converters Lens Construction: