Sigma 200-500mm f/2.8 APO EX DG Ultra-Telephoto Zoom Lens for Canon DSLR Cameras Ultra telephoto zoom lens; fast aperture of F2.8 at the 500mm and F5.6 at the 1000mm focal length Dedicated "Attachment" ensures autofocusing at the 1000mm focal length SLD and three ELD glass elements provide high image quality from the maximum large aperture Supplied with 72mm filter holder at the rear For Canon digital SLRs