This lens represents a revolutionary leap forward in ease of use. This was achieved by transforming a large-aperture 300mm F2.8 lens into a zoom lens that allows you to determine the picture composition you want without having to change your vantage point. It has two SLD (the special low dispersion) glass elements in front group and another element of SLD is being used for rear group for excellent correction of chromatic aberration. The new lens coating reduces flare and ghost, a common problem with digital cameras and also creates an optimum natural colour balance. It prides excellent imaging capability like a prime lens. The AF drive for Sigma SA, Canon and Nikon cameras is equipped with a silent, responsive and high speed HSM , which also provides full-time manual focus function. High-speed focusing is possible when this lens is used with dedicated APO EX tele-converters (1.4x and 2x). By adding an APO tele-converter, which is sold separately, you can use this lens as a 168-420mm F4 AF tele-zoom lens with a 1.4x tele-converter, or as a 240-600mm F5.6 AF ultra-telephoto zoom lens with a 2x tele-converter. It is also possible to use AE (Automatic Exposure) function, even EX Tele-converters are attached to the lens.
