The Sigma 70-200 f2.8 EX DG OS HSM Lens for Canon has a wide aperture telephoto zoom lens incorporating Sigma’s original Optical Stabiliser function. It covers focal lengths from 70mm to 200mm and offers a constant aperture of F2.8 over the entire zoom range. The Optical Stabilizer function on the Sigma 70-200 f2.8 EX DG OS HSM Lens offers the use of shutter speeds approximately 4 stops slower than would otherwise be possible, which makes shooting easy for many types of photography such as portraits and sports. The two “F” Low Dispersion (FLD) glass elements in the Sigma 70-200 f2.8 EX DG OS HSM Lens for Canon have a performance equal to fluorite glass, and three Special Low Dispersion (SLD) glass elements provide excellent correction of colour aberration. Sigma's excellent multi layer coating, will also help with ghosting and lens flare. The Sigma 70-200 f2.8 EX DG OS HSM Lens for Nikon incorporates Hyper Sonic Motor (HSM) ensuring a quiet and high speed auto focus, as well as full-time manual focus capability. The Sigma 70-200 f2.8 EX DG OS HSM Lens for Canon has a compact construction with a diameter of 86.4mm (3.4in.) and overall length of 197.6mm (7.8in.). It has a weight of 1,430g (50.4oz.). The compact and lightweight construction makes it ideal for many types of photography such as portrait taking, landscapes and sports. It is also possible to attach Sigma’s optional APO Tele Converters to the Sigma 70-200 f2.8 EX DG OS HSM Lens.