The staple Sigma 50mm 1.4 DG HSM has been redesigned and re-engineered to set a new standard for the Art line. With a large 1.4 aperture, the Sigma 50mm 1.4 prime lens is a pro level performer for shooting everything including portrait photography, landscape photography, studio photography and street photography. A Hyper Sonic Motor (HSM) ensures quiet, smooth and accurate auto-focusing and paired with Special Low Dispersion (SLD) glass and Super Multi-Layer coating, the 50mm 1.4 is a high performance lens for the modern DSLR sensors. 13 elements in 8 groups allow for unsurpassed performance even at wide apertures and close-up photography is easily managed with a minimum focusing distance of 40cm. The Sigma 50mm 1.4 lens is the new exceptional standard, standard prime.USB Dock Compatibility : Sigma has developed special software (SIGMA Optimization Pro) that can update the lens firmware and adjust parameters such as focus.