The EF 24-70mm f/2.8L II USM is a Canon L-series zoom commonly thought of as the workhorse of lenses. Ranging from wide-angle to portrait length, this lens is also distinguished by its constant f/2.8 maximum aperture to benefit working in difficult lighting conditions and to afford greater control over the depth of field. The lens is also characterized by its sophisticated optical design, which includes one Super UD element and two UD elements, which reduce color fringing and chromatic aberrations in order to realize a high degree of color accuracy and clarity. Three aspherical elements are also featured, and minimize distortion and spherical aberrations for improved sharpness. this 24-70mm f/2.8 also sports a ring-type USM and internal focusing mechanism to enable quick, quiet, and accurate autofocus performance, as well as full-time manual focus override. Bright constant f/2.8 maximum aperture affords consistent illumination throughout the zoom range and also affords greater control over the depth of field for working with selective focus techniques. Three aspherical elements minimize spherical aberrations and distortions for improved sharpness and accurate rendering. The rounded nine-blade diaphragm contributes to a pleasing out-of-focus quality that benefits the use of shallow depth of field and selective focus techniques.