From the ManufacturerHigh performance, large aperture medium telephoto macro lens with OS (Optical Stabilizer).High performance, large aperture medium telephoto macro lens with OS (Optical Stabilizer). SLD glass provides good control of aberration and the floating inner focus system ensures high rendering throughout the focusing range. By using Sigma's APO Tele Converter, it is possible to take photos at greater than 1:1 magnification. HSM ensures a quiet and high speed AF as well as full-time manual focus override. This lens has a rounded 9 blades diaphragm which creates an attractive blur to the out of focus areas. Large aperture medium telephoto macro lensThis medium telephoto macro lens allows you to maintain an appropriate distance from subjects while still getting close up photos. Since the working distance at its closest focusing position is 142mm, shadows of the lens and camera will not affect photography making it suitable for taking photos of subjects, such as flowers, under natural lighting conditions. In comparison to the Sigma 50mm and 70mm macro lenses, the main subjects can be defined with perfectly smooth and blurred backgrounds. No Super Multi-Layer Coating (left). With Super Multi-Layer Coating (right). High rendering performanceThe lens power layout produces excellent optical performance. High refractive index SLD (Special Low Dispersion) glass corrects chromatic aberration, spherical aberration and field curvature. It ensures high rendering performance at all shooting distances. The Super Multi-Layer Coating reduces flare and ghosting, maintaining quality images with high contrast. No Optical Stabilizer (top). With Optical Stabilizer (bottom). Handheld photography with easeSigma's OS (Optical Stabilizer) system offers effective correction of approximately 4 stops. As the stabilization effect is visible through the viewfinder, it aids composition and accurate focusing.* The OS effectiveness will gradually decrease as the shooting distance becomes shorter. Floating inner focusingThis lens incorporates floating inner focusing which moves two lens groups separately. This minimizes aberrations which occur as shooting distance changes, and enables stable rendering of the image from infinity to 1:1 magnification. This also corrects image distortion, especially when taking close-up pictures. Since focusing does not change its overall length, this lens is easy to hold and use. Hyper Sonic Motor Quiet and speedy AFHSM indicates lenses equipped with a Hyper Sonic Motor, driven by ultrasonic waves. HSM provides quiet and high speed AF. It is also possible to use full-time manual focus, even if the lens is set to autofocus. Rounded 9 blades diaphragmThis lens has a rounded 9 blade diaphragm which creates an attractive blur to the out of focus areas. This also creates smooth, rounded out of focus highlights when taking photos which have a strong light source in the background such as lights shining on the surface of water. Lens ConstructionIn a conventional lens, focusing requires an extension of the entire lens or the front lens group. However, to better accommodate autofocusing mechanisms and closeup photography, a need has arisen for lenses that do not change their length during focusing or suffer from focus-dependent variation in aberration. Therefore, Sigma has developed focusing systems that only move elements within the lens barrel. These incorporate smaller and lighter moving lens elements which help improve auto-focus speed. With their unchanging barrel length and small variation in the center of gravity, these lenses also enhance balance and stability for the photographer. Furthermore, since the front of the lens does not rotate, polarizing filters can be used with extra convenience. Specifications Lens Construction 16 Elements in 11 Groups Angle of View 23.3 degrees Number of Diaphragm Blades 9 Blades (Rounded diaphragm) Minimum Aperture F22 Minimum Focusing Distance 31.2cm / 12.3in. Maximum Magnifi