High Magnification Ultra Telephoto Zoom Lens, with a 10x zoom ratio from 50mm to 500mm, optimized for digital SLR cameras. This high zoom ratio lens is optimized for digital SLR cameras and capable of covering a wide range of focal lengths from 50mm standard to 500mm ultra telephoto. This ultra-zoom lens employs a seven-group zoom system, which provides a high zoom magnification of 10x. Triple-cam Rear Focusing System ensures high precision throughout the whole focus range. The new lens coating reduces flare and ghost, which is a common problem of digital cameras and also creates an optimum colour balance. It is possible to reach 1000mm focal length by using the Sigma 2X Apo Tele Converter By attaching the 2X APO EX Tele-Converter, this lens can be used as a 200-1000mm/F10.4-12.6 manual focus zoom lens, while maintaining a very compact size for 1000mm focal length. It is also possible to use AE (Automatic Exposure) function, when EX Tele-converters are attached. The APO lens corrects chromatic aberrations An apochromatic lens, which keeps color aberration to a minimum, using Special Low Dispersion (SLD) or Extraordinary Low Dispersion (ELD) glass is called an APO series lens at Sigma. This lens uses four pieces of SLD (the special low dispersion) glass for excellent correction of chromatic aberration. High optic performance is demonstrated throughout the entire zoom range. HSM (Hyper Sonic Motor) The HSM models (the HSM is only available for AF Canon, Nikon and Sigma Mounts) provide quiet high-speed AF function, as well as full time manual focus capability. Easy Operation and Handling This lens also features a Zoom Lock device to eliminate Zoom Creep when the lens is tilted down. When the lens is set to the 50mm focal length, it is remarkably compact and provides easy handling. The tripod mount is composed of magnesium, to minimize total weight and also it is easy to grip and carry the lens due to ergonomic design of the tripod mount.