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 color balance. This lens uses four pieces of SLD (the special low dispersion) glass for excellent correction of color aberration. A zoom lock switch eliminates "zoom creep" during transportation, a convenient addition when traveling. The HSM Hyper Sonic Motor models provide quiet high-speed AF function, as well as full-time manual focus capability., The rear focus mechanism produces a non-rotating front lens elementwhich accepts a bayonet "Petal-type Hood", which prevents extraneous light from degrading the image quality. By adding an APO teleconverter (sold separately), you can use this lens as a 140-700 .... ..7.3-8.8 MF ultra-telephoto zoom lens with a 1.4X EX teleconverter, or as a 200-1000mm F10.4-12.6 MF ultra-telephoto zoom lens with a 2X teleconverter. .. Teleconverters can be used in 100mm 500mm focal length range..