This Sigma 120-400mm f/4.5-5.6 DG OS HSM APO Lens is an ultra telephoto zoom lens ideal for nature/outdoor or sports photography. This translates into an equivalent range of 192-640mm when used with an Canon digital SLR camera.

The OS (Optical Stabilizer) system minimizes image blur caused by camera shake, and offers the equivalent of shooting at a shutter speed 3-4 stops faster. This allows handheld telephoto zoom shooting even in poorly lit conditions.

The use of the OS (Optical Stabilizer) system, HSM (Hyper Sonic Motor), APO apochromatic design, three elements of SLD (Special Low Dispersion) glass, and multicoated optics all enable this lens to provide a high level of performance throughout its entire zoom range, as well as versatility. A rear focus system insures quick, convenient manual focus and a non-rotating front barrel.

The improved DG lens design corrects for various aberrations. This lens is specially coated to get the best color balance, while cutting down on ghosting caused by reflections from the digital image sensor. The lens provides the utmost correction against lateral chromatic aberration, which is a serious problem for digital SLR cameras.

By adding the optional Sigma APO teleconverter, you can use this lens as a 168-560mm f/6.3-8 manual focus ultra-telephoto zoom lens with a 1.4X EX teleconverter, or as a 240-800mm f/9-11 manual focus ultra-telephoto zoom lens with a 2X teleconverter.

The OS system uses two sensors inside the lens to detect vertical and horizontal movement of the camera. It works by moving an optical image stabilizing lens group, to effectively compensate for camera shake. It automatically detects movement of the camera and compensates for camera shake when shooting moving subject such as motor sports.

The HSM (Hyper Sonic Motor) system ensures quiet and high-speed auto focusing with full time manual focus override.

Three Special Low Dispersion (SLD) elements provide excellent correction for chromatic aberration.

Super Multi Layer (SML) coating reduces ghost and flare.

The lens design incorporates an inner focusing system, which prevents the front of the lens from rotating, thereby making it particularly suitable for use with circular polarizing filters and petal shaped lens hoods.