This Sigma 150-500mm f/5-6.3 DG HSM APO Lens is an ultra telephoto zoom lens ideal for nature, wildlife, or sports photography. This zoom range translates into an equivalent range of 225-750mm when used with a Sony digital SLR camera (with APS-C-size sensor). The use of 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 210-700mm f/7-9 manual focus ultra-telephoto zoom lens with a 1.4X EX teleconverter, or as a 300-1000mm f/10-13 manual focus ultra-telephoto zoom lens with a 2X teleconverter. ? 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.