The APO MACRO 150mm F2.8 EX DG OS HSM is a large aperture medium telephoto macro lens. As the successor to the APO MACRO 150mm F2.8 EX DG HSM, which was first introduced in October 2004, the new version now includes the OS technology and a weather-resistant design that is for convenient outdoor use. A floating focusing system in the 150mm 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. The lens also contains three SLD glass elements for correction of all aberrations, Super Multi-Layer Coating, and HSM. To locate an authorized Sigma dealer near you, visit www.sigmaphoto.com.