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 This ultra telephoto zoom lens offers a fast aperture of F2.8 at the 500mm focal length and F5.6 at the 1000mm. It covers widely-used focal lengths from 200mm to 500mm and has a large aperture of F2.8 throughout the entire zoom range. This lens can be used to create amazing image expression with various types of photography such as astrophotography, portraits, wildlife, sports. SLD (Special Low Dispersion) glass and three ELD (Extraordinary Low Dispersion) glass elements provide excellent correction for all type of aberrations. The super multi-layer coating reduces flare and ghosting and provides high image quality from the extremely large aperture. The lens hood, designed exclusively for this lens, blocks out extraneous light. A 72mm filter can be inserted at the rear of the lens, and a circular polarizing filter can be used in situ thanks to the ingenious internal rotation mechanism. The dedicated Li-ion battery BP-21 is used to power the zooming and AF operation. This battery is built in the lens barrel. For the convenience of the photographer, focusing distances and focal lengths can be viewed on the lens' built-in LCD panel.