The sigma 150mm f28 ex dg os hsm macro lens features the latest optical technology a floating focusing system moves two different lens groups in the optical path to different positions and compensates for astigmatic aberration and spherical aberration and provides extremely high optical performance from infinity to 11 macro equipped with sigmas proprietary os optical stabiliser function the 150mm f28 ex dg os hsm macro lens offers the use of shutter speeds approximately 4 stops slower t