The EF 70-200mm f/2.8L IS III USM from Canon is an L-series telephoto zoom distinguished by its bright design and advanced optics. Ideal for a variety of subjects ranging from portraiture to sports, the fast constant f/2.8 maximum aperture excels in difficult lighting conditions and also offers increased control over the depth of field for isolating subjects. The optical layout makes use of one fluorite element and five UD elements to suppress chromatic aberrations and color fringing in order to realize a high degree of clarity throughout the zoom range.  A ring-type USM and internal focusing mechanism also afford quick, quiet, and accurate autofocus performance, as well as a full-time manual focus override. Additionally, this lens is weather-sealed for use in trying environmental conditions. Bright constant f/2.8 maximum aperture affords consistent performance throughout the zoom range and offers notable control over the depth of field for working with selective focus techniques. An Air Sphere Coating (ASC) has been applied to lens elements to reduce backlit flaring and ghosting for maintained light transmission and high contrast in strong lighting conditions. A ring-type Ultrasonic Motor (USM), along with an internal focusing system, is employed to deliver fast, precise, and quiet autofocus performance as well as full-time manual focus override. The rounded eight-blade diaphragm contributes to a pleasing out-of-focus quality that benefits the use of shallow depth of field and selective focus techniques.