The Sigma 17-50mm f/2.8 EX DC HSM Zoom Lens for Sony DSLRs with APS-C Sensors is a versatile, lightweight, and compact lens designed specifically for Sony A-mount and Minolta digital SLR cameras with APS-C size sensors. The lens has a fast f/2.8 maximum aperture throughout the entire zoom range and its 35mm focal length equivalency is 25.5 - 75mm. It features a construction of 17 elements in 13 groups with glass that corrects for aberrations and multi-layered lens coating to minimize flare and ghosting. It produces high contrast, sharp images throughout the zoom range even at its maximum aperture.