Pairing a versatile range of telephoto focal lengths with a fast constant maximum aperture, this 50-100mm f/1.8 DC HSM Art Lens from Sigma is designed for APS-C-format sigma DSLRs, and provides an 80-160mm equivalent focal length range. The bright constant maximum aperture offers consistent low-light performance throughout the zoom range and also affords greater control over focus placement for shallow depth of field and selective focus applications. Complementing the versatile telephoto range is a sophisticated optical design that incorporates three F Low Dispersion elements, one Special Low Dispersion element, and one high-refractive index, high-dispersion glass element. This combination of low dispersion designs works to noticeably reduce chromatic aberrations and color fringing throughout the zoom range, as well as deliver a high degree of contrast and clarity. Additionally, a Super Multi-Layer Coating has been applied to lens elements to reduce lens flare and ghosting to benefit working in strong lighting conditions. An unprecedented combination of focal length and speed, this 50-100mm f/1.8 lens offers a variety of favored telephoto perspectives in combination with a flexible maximum aperture.,,Complementing the imaging capabilities is a refined physical construction with internal focus and zoom mechanisms to limit the overall length of the lens during use. A Hyper Sonic AF motor affords quick focusing speeds and quiet performance as well as the ability to manually override focus at any time for greater control. Also suiting quick shooting applications, the nine-blade diaphragm has been constructed from fluorine-coated polycarbonate, along with a carbon feather film for exceptionally smooth, controlled performance when photographing at high shooting speeds. Contrasting this, a tripod collar is integrated into the design, too, for greater stability when working atop a tripod or monopod.