NOW SUPPLIED WITH 3 YEARS MANUFACTURERS WARRANTY AND FREE LENS CARRYING CASE & LENS HOOD!Superior optical performance This telephoto zoom lens has a large maximum aperture of f2.8 that is constant through the zoom range. It is very popular among professional and amateur photographers. SLD glass for superior optical performance This lens uses two pieces of SLD (the special low dispersion) glass in the front lens group and another two in the rear group for excellent correction of chromatic aberration. High optical performance is demonstrated throughout the entire zoom range. HSM (Hyper Sonic Motor) for silent and fast auto - focus 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. Inner focusing and inner zooming systems This lens incorporates an inner focusing system- which eliminates front lens rotation- allowing the use of a Petal-type Hood and more convenient to use of circular polarizing filter. Since focusing and zooming do not change its overall length- this lens is easy to hold and use. This lens comes with detachable tripod mount. APO Tele-Converter EX (optional) High-speed focusing is possible when this lens is used with dedicated APO EX tele-converters (1.4x and 2x). With APO EX tele-converter 1.4x EX- it works as an AF tele-zoom lens from 98mm to 340mm F4. With APO EX tele-converter 2x EX- it works as an AF tele-zoom lens from 140mm to 400mm F5.6. It is also possible to use AE (Automatic Exposure) function- when EX Tele-converters are attached. Lens SpecificationLens Construction  17 Elements in 14 Groups Angle of View   34.3 - 12.3 degrees Number of Diaphragm Blades   9 BladesMinimum Aperture  F32 Minimum Focusing 180cm Maximum 1:7.8 Filter Size  77mm Dimensions  Diameter 86.2mm X Length 184mm Weight   1270g SRP  ?799.99 Corresponding Mounts -  SIGMA CANON NIKON (D) MINOLTA (D) PENTAX NOW SUPPLIED WITH 3 YEARS MANUFACTURERS WARRANTY AND FREE LENS CARRYING CASE & LENS HOOD!