The Sigma 17-70mm f/2.8-4 DC Macro OS HSM Lens for Sigma is a standard zoom lens designed especially for DSLRs with APS-C-sized image sensors. This lens has a 35mm-equivalent focal length range of 25.5-105mm, providing wide-angle to portrait-length angles of view for use in everyday shooting situations. This lens features a fast f/2.8-4 maximum aperture to help better control your focus plane and to aid in low-light shooting. A built-in Optical Stabilizer also helps in low-light situations by providing a four-stop reduction in the appearance of camera shake, which is ideally suited for macro and telephoto shooting as well. The Hyper Sonic AF Motor delivers fast, smooth, and quiet auto focusing that greatly benefits video applications. The integration of two FLD, one SLD, and three aspherical lenses in the construction helps to reduce the effects of chromatic and chromatic axial aberrations, and Super Multi-Layer coated elements help to increase contrast for sharp, clear imagery. As part of Sigma's new Contemporary line of lenses, this lens is designed using Thermally Stable Composite (TSC) materials to help reduce the overall weight and size of the lens barrel by about 30% without compromising on optical integrity, rigidity, or overall durability. For updating lens firmware and fine-tuning its nuances to best-suit your personal shooting, this lens is compatible with the Sigma USB Dock. The dock allows you to specify certain parameters and other settings through the Sigma Optimization Pro software, such as AF speed and focusing limitations.