The sigma 17 70mm f28 4 dc macro os hsm lens canon fit is an all purpose standard zoom lens specifically for digital slr cameras with an aps c sized sensor the sigma 17 70mm offers everything from sweeping landscapes to stunning portraits while keeping the size of the lens compact and easily portable the hyper sonic motor hsm ensures quiet accurate and fast autofocusing while the os optical stabiliser compensates for camera shake when shooting by hand the construction of the 17 70mm i