Covering a flexible ultra-wide range, the Canon EF-mount 10-20mm f/3.5 EX DC HSM from Sigma is a versatile zoom well-suited for landscape, architectural, and interior photography. The lens's optical design incorporates a series of low dispersion and aspherical elements, which help to reduce chromatic and spherical aberrations throughout the zoom range, as well as contribute to improved sharpness and clarity. A Super Multi-Layer Coating is also used to suppress flare and ghosting for improved contrast and color accuracy. Benefitting the imaging attributes, a Hyper Sonic Motor also affords quick and quiet autofocus performance as well as full-time manual focus override.Wide-angle zoom is designed for APS-C-format Canon EF-mount cameras and provides a 16-32mm equivalent focal length range.Constant f/3.5 maximum aperture is suitable for working in available light conditions.Two Extra-Low Dispersion (ELD) elements and one Special Low Dispersion (SLD) element are featured in the optical design, and help to reduce color fringing and chromatic aberrations for improved clarity and color accuracy.Four aspherical elements are used to help limit distortion and spherical aberrations and also contribute to greater overall sharpness and accurate rendering.Super Multi-Layer Coating has been applied to individual elements to minimize flare and ghosting for improved contrast and color accuracy when working in strong lighting conditions.Hyper Sonic Motor (HSM), along with an internal focusing design, realizes quick and quiet autofocus performance as well as full-time manual focus override.Minimum focusing distance of 9.4" is available throughout the zoom range.Seven-blade diaphragm contributes to a pleasing bokeh quality.