Manufacturer description: The Sigma 17-50mm F2.8 EX DC OS HSM is a useful large-aperture standard zoom lens designed exclusively for APS-C format digital SLRs. Covering a focal range of approximately 25-75mm, the 17-50mm features OS optical stabilization, and a HSM ultrasonic-type focus motor. With a minimum focusing distance of 11 inches throughout the entire zoom range this lens offers a useful semi-macro close up capability, for a maximum reproduction ratio of 1:5.