The Sigma 40mm f/1.4 DG HSM Art Lens is a wide normal-length lens characterized by a bright design and sophisticated optical layout. The fast f/1.4 maximum aperture helps to achieve shallow depth of f espandi...ield and selective focus effects, and also suits working in difficult lighting conditions. The optical design incorporates a series of low dispersion and aspherical elements, which help to improve sharpness and clarity by controlling both spherical and chromatic aberrations.