From the ManufacturerCompact large aperture standard zoom lens equipped with HSM for the latest digital SLR camerasThis large aperture standard zoom lens covers focal lengths from 24mm and is housed in a compact construction. The latest optical design provides a compact construction and is ideal for general photography. ELD (Extraordinary Low Dispersion) glass, two SLD (Special Low Dispersion) glass elements and three aspherical lenses provide excellent correction of all types of aberrations. This lens incorporates HSM (Hyper Sonic Motor), ensuring a quiet and high speed AF as well as full time manual focus capability. This lens has a minimum focusing distance of 38cm/15in and a maximum magnification ratio of 1:5.3. The rounded 9 blades diaphragm creates an attractive blur. Excellent optical performanceELD (Extraordinary Low Dispersion) glass, two SLD (Special Low Dispersion) glass elements, two molded glass aspherical lenses and a hybrid aspherical lens provide excellent correction for all type of aberrations. High image quality is assured throughout the entire zoom range. Large aperture standard zoom lens with compact constructionThe lens has a compact construction with an overall length of 94.7mm (3.7"). It is ideal for many situations such as portrait, landscape and general photography. F2.8 large aperture over the entire zoom rangeThis lens offers a large aperture of F2.8 over its entire zoom range. It provides freedom of creative expression and is ideal for photography indoors or in dim lighting. Hyper Sonic Motor HSM (Hyper Sonic Motor)HSM indicates lenses equipped with a Hyper Sonic Motor, driven by ultrasonic waves. HSM ensures a quiet and high speed AF as well as full-time manual focus override by rotation of the focus ring. Inner focusing systemThe polygonal shape of a conventional iris diaphragm causes outo-focus light points to appear polygonal. A rounded diaphragm is designed to produce rounded outo-focus light points when opened to near maximum aperture. This creates attractive bokeh effects in many situations, such as when photographing a subject against an out-of-focus surface of water from which light is being reflected. No Super Multi-Layer Coating (left). With Super Multi-Layer Coating (right). Reduced Flare and GhostingSigma's own Super Multi-Layer Coating suppresses flare and ghosting by preventing reflections within the lens. All DG and DC lenses in the current Sigma range feature this original technology. In digital cameras, flare and ghosting may also be caused by reflections between the image sensor and lens surfaces. Here too, Sigma's Super Multi-Layer Coating is highly effective, assuring images of outstanding contrast. Petal-type hood This lens is equipped with a Petal-type hood to block out extraneous light and reduce internal reflections. 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. Lens Construction 14 Elements in 12 Groups Angle of View 84.1 -34.3 degrees Number of Diaphragm Blades 9 Blades Minimum Aperture F22 (Rounded diaphragm) Minimum Focusing Distance 38cm / 15.0in. Maximum Magnification 1:5.3 Filter Size Diameter 82mm Dimensions Diameter 88.6mm x Length 94.7mm / 3.5in. x 3.7in. Weight 790g / 27.9oz. MTF ChartView Larger ImageMTF (Modular Transfer Func