The Sigma APO 120-300mm F2.8 EX DG HSM a truly unique product which is a rarity in the photo industry. This lens is the only lens of its kind on the market; a professional zoom lens that also features a fast aperture. Most professionals own the standard 300mm 2.8, but they also have to carry a shorter zoom lens for those times when the subjects move closer. That means fumbling around switching lenses or carrying a second camera body. The amazing Sigma zoom lens let you instantly determine the picture composition you want without having to change your vantage point. Imagine photographing courtside at a college basketball game and having the versatility to zoom in on a player’s face or hand and then instantly zoom back to capture the entire player making his shot. You can do it with the Sigma APO 120-300mm F2.8 EX DG HSM. The aperture remains constant at F2.8 throughout the entire zoom range.