This document summarizes the Canon 70-200mm f/2.8L EF Telephoto Zoom Lens USM. It has an 18 element, 15 group lens construction with a focal length range of 70-200mm and a constant maximum aperture of f/2.8. It features 4 UD glass elements to correct chromatic aberrations and is one of Canon's finest telephoto zoom lenses, comparable in quality to a prime lens. Its constant f/2.8 aperture and superb image quality make it a popular choice for professionals where image quality is important.