Truly a revolutionary product, the Sigma 18-35mm 1.8 DC HSM is the first wide-angle to standard zoom lens to achieve a large aperture of 1.8. Designed specifically for APS-C sized sensors, the Sigma 18-35mm 1.8 translates to 27mm-52.5mm on 35mm camera. Tapping into Sigma?s long history of lens innovations, the 18-35mm 1.8 DC HSM incorporates a wide glass molded aspherical lens with Special Low Dispersion (SLD) glass to compensate for aberrations and curvature at the widest angle. Internal focusing and zooming allows for more usability and functionality. The 18-35mm is ideal for landscape photography, portrait photography, still life photography, snap shots, casual photography, and close-ups and the Hyper Sonic Motor (HSM) ensures smooth, fast and accurate autofocusing. The use of Thermally Composite Material (TSC) reduces size and weight but increases accuracy of the lens construction. Its new Global Vision design works features compatibility with the Sigma USB dock for further customization. A 9 blade rounded diaphragm also creates beautiful background blur. The Sigma 18-35mm 1.8 DC HSM is a new benchmark in photographic history and a must have for every camera bag. SPECIFICATIONS Lens Construction 17 Elements in 12 Groups Angle of View (SD1) 76.5?-44.2? Number of Diaphragm Blades 9 Mininum Aperture f16 Minimum Focusing Distance 28 cm/ 11.0 in Filter Size (mm) 72mm Maximum Magnifications 1:4.3 Dimensions(Diameter x Length) 78mm x 121.0mm/3.1in. x 4.8in. Weight 28.6oz