This telephoto zoom lens incorporates Sigma 39;s original OS Optical Stabilizer function. It offers the use of shutter speeds approximately 4 stops slower. Three SLD Special Low Dispersion glass elements provide excellent correction for chromatic aberration. This lens is equipped with the rear focus system that minimizes fluctuation of aberration caused by focusing. It provides optimum image quality throughout the entire zoom range. The super multi layer coating reduces flare and ghosting. High image quality is assured throughout the entire zoom range. The minimum focusing distance of 150cm 59.1 throughout the entire zoomrange and has a maximum magnification of 1:4.2 make it useful for close up photography. This lens incorporates HSM Hyper Sonic Motor , which ensures a quiet and high speed AF as well as full time manual focusing capability. The addition of the optical 1.4x EXDG APO or 2x EX DG APO Tele Converters produce a 168 560mm F6.3 8 MF ultra telephoto zoom lens or a 240 800mm F9 11 MF ultra telephoto zoom lens respectively.