f/1.4 aperture for shallow depth of field Works on APS-C or Full Frame models Quick, quiet HSM focus motor The Sigma 50mm f/1.4 DG HSM A is a prime lens suitable for portrait and street photography, as well as low light shooting and action. The bright aperture makes the lens capable of rapid focussing, shallow depth of field and capturing images in limited light, making it an excellent all round lens for a roaming portrait photographer capturing candid images. As part of the Art range of lenses by Sigma, the 50mm f/1.4 DG HSM is capable of taking artistic shallow depth of field images, blurring backgrounds out in an attractive manner. The super low dispersion glass prevents chromatic aberration from becoming an issue, which can appear as purple fringing and the HSM focus motor is both quick and quiet. The Sigma 50mm f/1.4 DG HSM A replaced the 50mm F1.4 EX DG HSM, redesigning the optics and casing of the lens to produce a model which suits portrait and wedding photographers, as well as those shooting candid images on the streets.