"Sigma 18-35mm F/1.8 DC HSM ART Lens, 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 Sigma 18-35mm is ideal for landscapes, portraits, still life, snap shots, casual, 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 the lens durability. Its new Global Vision design works with its 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. USB Dock Compatibility Sigma has developed special software (SIGMA Optimization Pro) that can update the lens firmware and adjust parameters such as focus. (USB Dock is sold separately)|This lens is part of Sigma's Art line; deeming it well-suited to creative image making due to its large, constant f/1.8 maximum aperture and ability to produce aesthetic bokeh by way of a nine-blade circular diaphragm|One aspherical lens element, as well as the incorporation of SLD glass, help to minimize the appearance of distortions and aberrations throughout the zoom range and provide clear imagery with enhanced sharpness|The Hyper Sonic Motor provides fast, quiet and smooth auto focusing that is well-suited for use with video applications. This AF motor can also be manually overridden at any time by rotating the focusing ring, giving you the ability to fine-tune imag|Constructed using a TSC compound material, this lens is lightweight while also exhibiting notable durability and resistance to environmental changes|An internal focusing and zooming mechanism helps to maintain a consistent overall lens length and a non-rotating front ring facilitates more efficient use of circular polarizers|Compatible with Sigma's USB Dock and Sigma Optimization Pro software for fine-tuning your lens' performance, updating its firmware and better suiting it to your needs"