Sigma APO 300mm f2.8 EX is one of the EX Series lenses. It is an ultra compact Apochromatic telephoto lens with a fast F2.8 maximum aperture, and incorporates two Extraordinary Low Dispersion glass elements (Abbe number 90.3), to reduce chromatic aberration to a minimum. It incorporates internal focusing which enables responsive and fast auto focus speed. The AF drive for Sigma SA, Canon and Nikon S.L.R. cameras feature Sigma's ultra-quiet Hyper Sonic Motor (H.S.M.). Sigma's dedicated APO EX Tele Converter 1.4x and 2x lenses work easily with this lens without sacrificing the AF speed of the Sigma APO 300mm F2.8 EX. A detachable tripod socket and rotatable drop in filter holder are provided. The lens materials used in this new lens are lead and arsenic free ecological glass.