The Canon EF 70-200mm f/2.8 L USM is a large aperture professional grade telephoto zoom lens. Being an L Series lens, maximum attention was been given to sharpness, contrast, color reproduction, & bokeh by the designers.
The heart of the lens is an optical system consisting of 18 elements in 15 groups; Four Ultra Low Dispersion UD glass elements are strategically placed to maximize image quality. All lens elements are free of lead. A large f/2.8 maximum aperture allows light gathering capability superior to most telephoto & zoom lenses and consequently allows acesss to faster shutter speeds.
Portrait Photographers, sports photographers, pet photographers, wedding photographers, photojournalists, wildlife photographer, other action photographers and nearly everyone else wants fast autofocus and Canon delivers it with an internal focus system connected to a ring type Ultrasonic Motor. The focus mechanism is designed to provide the photographer the option of instant manual focus override without touching the lens AF control button, manual focus override works full time (even without power to the lens). The zoom and focus grips have different patterns and widths to aid tactile differentiation. A focus limit switch allows selection of a narrower 3 meters to infinity focus range to significantly reduce autofocus time as closer focussing distances occupy an amount of focus travel that is proportionally much greater than in farther focus distances. The full focus range of the lens is 1.5 meters to infinity.
A removable tripod mount is standard equipment and it rotates for easier vertical photography on a tripod or monopod.
The EF 70-200mm f/2.8 L USM is a less expensive, less mechanically complex, alternative to Canon's Image Stabilized L series lenses. Image Stabilization can't compensate for subject matter motion, so the lens remains a popular value among monopod supported sports shooters who require very fast shutter speeds, and among photographers using solid tripod rigs (the original form of image stabilization).