The Sigma 24-70mm f/2.8 DG OS HSM Lens covers a useful wide-angle to portrait-length range of focal lengths to suit shooting in a variety of environments. As part of the esteemed Art series of lenses, espandi... a sophisticated optical design is used that incorporates three SLD elements and four aspherical elements to reduce chromatic and spherical aberrations, as well as color fringing, distortions, and other anomalies for greater clarity and sharpness.