The Sigma's 12-24mm f/4.5-5.6 DG HSM II Lens is designed for use with full-frame digital cameras, and offers a dramatically ultra-wide, minimally distorted zoom lens with a field of view from 122° to 84.1°. This range makes it ideal for the tightest of interiors, as well as for dramatic landscape photography. Using a camera with an APS-C sensor will give you an effective range of 17-35mm, also a very attractive wide-angle zoom range. One Special Low Dispersion (SLD) glass element and four "F" Low Dispersion (FLD) glass elements compensate for color aberration and deliver improved image quality. Three glass mold elements and one hybrid aspherical lens give you compact, lightweight construction (3.3" diameter x 4.7"/23.6 oz) and improved performance.