Sigma 17-50mm f/2.8 EX DC OS HSM Lens for $544 – Deal Alert March 12, 2013 By Eric Reagan B&H has the Sigma 17-50mm f/2.8 EX DC OS HSM lens for $544 (reg. $669) through March 17. It’s available in Canon, Nikon, Pentax, Sony and Sigma mounts for APS-C format cameras. Check it out here at B&H Photo.