The APO Macro Sigma 180mm F2.8 EX DG OS HSM is a high performance telephoto macro lens designed for Full Frame sensors but may also be used with smaller APS-C size sensors with a corresponding effective increase in focal length to about 260mm with most cameras. The 180mm F2.8 has a large aperture to handle any lighting scenario and the macro capabilities allow focusing down to 1:1 magnification ratio at its closest working distance of 18.5 inches. A Hyper Sonic Motor (HSM) ensures quiet, high speed, and accurate autofocusing while an Optical Stabilizer (OS) compensates for camera shake when shooting hand held. The 180mm F2.8 macro also incorporates a floating Internal Focusing system which reduces aberration during shooting working together with three FLD ("F" Low Dispersion) glass elements for superior correction of color aberration. This lens has a rounded 9 blade diaphragm creating an attractive blur to the out of focus areas of the image and is also compatible with Sigma APO teleconverters.