Tamron's fast telephoto SP AF300mm F/2.8 LD (IF) delivers remarkable and exacting performance demanded by professionals. Two large LD (Low Dispersion) elements in the front lens group provide high contrast and crystal-clear image quality from the full open aperture. With Internal Focusing, you can maintain optimum holding balance since the lens' overall length remains constant during focusing. Our Floating Focusing System improves optical performance especially at close shooting distances. Nine specially-shaped aperture blades form a nearly perfect circle to create excellent background blur for outdoor portraits. The true value of this lens is apparent when photographing sports action, low light theater performances, and wildlife. New is a Canon version that provides an easy-to-use AF/MF focusing ring, rear filter insertion frame that is compatible with the standard accessory circular polarizing filter and with the ring rotation capability from outside the lens, and detachable tripod mounting stand.