The Sigma APO MACRO 150mm F2.8 EX DG OS HSM is a large aperture medium telephoto macro lens which incorporates Sigma’s original Optical Stabilizer function. The successor to the APO MACRO 150mm F2.8 EX DG HSM, introduced to market in October 2004, offers the latest optical design technology and weather-resistant design throughout for use in harsh conditions. A floating focusing system moves two different lens groups in the optical path to different positions. This system compensates for astigmatic aberration and spherical aberration and provides extremely high optical performance from infinity to 1:1 Macro. Three SLD (Special Low Dispersion) glass elements provide excellent correction of all types of aberrations and the Super Multi-Layer Coating reduces flare and ghosting. This lens has superior peripheral brightness and provides sharp and high contrast images even at the maximum apertures. Equipped with Sigma’s own proprietary OS (Optical Stabilizer) function, this lens offers the use of shutter speeds approximately 4 stops slower than would otherwise be possible. The HSM (Hyper Sonic Motor) ensures quiet and high speed autofocus as well as full-time manual focus capability. This lens has a rounded 9 blade diaphragm creating a smooth blur to the out of focus areas of the image. It is also possible to use this lens with Sigma’s optional APO Tele Converters.