The APO Macro Sigma 180mm F2.8 EX DG OS HSM is high performance telephoto macro lens designed for full frame sensors but may also be used with smaller APS-C size sensors with corresponding effective increase in focal length to about 260mm with most cameras. 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. Hyper Sonic Motor (HSM) ensures quiet, high speed, and accurate autofocusing while an Optical Stabilizer (OS) compensates for camera shake when shooting hand held. 180mm F2.8 macro also incorporates 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 rounded 9 blade diaphragm creating an attractive blur to out of focus areas of image and is also compatible with Sigma APO teleconverters.