This high grade telephoto zoom lens responds to the exacting requirements of professionals and advanced amateurs, yet at a reasonable price. One artificial crystal fluorite and two UD (Ultra-low Dispersion) glass lens elements in its optical system eliminate secondary spectrum, which is often the Achilles' heel of telephoto lenses resulting lower picture quality. These elements assure high resolution and high contrast throughout the entire zoom range. The latest optical design gives a minimum focusing distance of 1.2m and 0.21x maximum magnification. This lightweight, compact zoom lens, having the same level of optical performance as EF 70 - 200mm f/2.8L USM, assures good portability and operability. The ring USM (Ultrasonic Motor) and inner focusing system achieves high-speed silent autofocusing. Manual focusing, even while in AF mode, is possible thanks to full-time manual focusing mechanism. Extenders EF 1.4X and 2X can be used with this lens, and the optional Ring Tripod Mount A (W) is being marketed concurrently.