"pentax 50mm lens" in Sigma 17-50mm F2.8 EX DC OS HSM

Sigma 17-50mm F2.8 EX DC OS HSM Prices, product details, cost, comparisons, online deals, features, photos, buy from Australia
For use with smaller chip APS-c digital cameras only Offers Sigma’s OS System (Optical Stabilization) allowing handheld photography even in low-light situation HSM (Hyper-Sonic Motor) ensures a quiet & high-speed auto focus FLD glass elements with performance equal to fluorite glass for compensate for color aberration Ultra compact with overall length of just 3.6”