The sigma 24-70mm f/2.8 If ex dg hsm lens is a large aperture standard zoom lens that covers a range from wide angle to short telephoto. It is ideal for general photography such as snapshots, portraiture and landscapes. When used on digital slr cameras which use the aps-c sony dt sensor, this lens will provide a focal length equivalent to 36-105mm in 35mm terms. Dg is a designation that sigma uses on lenses featuring optical systems designed to meet the performance characteristics of digital slr cameras. The super multi layer coating reduces flare and ghosting, and the use of eld and sld glass provides excellent correction of all types of aberrations. The hyper sonic motor hsm ensures a silent, high-speed af function as well as full-time manual focusing capability. Dg lens design the dg lens design corrects for various aberrations. The lens is specially coated to achieve the best color balance, while also cutting down on ghosting caused by reflections from the digital image sensor. Hsm hyper sonic motor hyper sonic motor provides smooth, silent af with fulltime manual focus override eld and sld elements this lens uses 1 eld extraordinary low dispersion element, 2 sld special low dispersion elements, and 3 aspherical elements for excellent correction of all types of aberrations ex series the ex series denotes excellence of engineering and technology 9-blade aperture the rounded 9-blade diaphragm opening makes out-of-focus elements appear more natural.