The Sigma 135-400mm f/4.5-5.6 APO DG Aspherical is a zoom lens that covers the most frequently used focal lengths, from mid to long-range telephoto. It is the ideal lens for shooting sports, nature, wildlife, landscapes and other types of photography that frequently use this telephoto range. The improved DG lens design corrects for various aberrations. This lens is specially coated to get the best color balance whilst 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. The advanced design incorporates a 5-group zoom system to achieve sharp, high contrast results throughout the entire zoom range One aspherical lens and three SLD (special low dispersion) elements for excellent correction of chromatic aberration Three SLD glass elements eliminate the secondary spectra effect normally associated with telephotos Rear focus system keeps the front lens from rotating, making it easier to use polarizing filters The rotating tripod mount can be conveniently detached if required