The Sigma 120-300mm f/2.8 EX DG OS APO HSM AF Lens (For Canon) provides a large constant f/2.8 maximum aperture at all focal lengths. In essence, it transforms a large-aperture 300mm f/2.8 lens into a zoom lens that allows you to determine the picture composition without having to change your vantage point. Optical image stabilization facilitates hand-held photography by allowing you to shoot at shutter speeds 4 stops slower than without the stabilization.
The use of Apochromatic design, SLD and FLD glass elements for correction of chromatic aberrations, and super multi-layers to reduce flare and ghosting deliver superb image quality. The autofocus drive is equipped with the silent, responsive and high speed Hyper Sonic Motor and internal focusing for a highly functional professional lens. The DG design makes it fully optimized for use with digital SLR cameras.