Sigma 50mm F1.4 EX DG HSM is an Auto Focus (AF) Standard Prime lens with 35mm FF max sensor coverage. When mounted on a 35mm FF sensor camera, it will give you an FF equivalent focal range of 50mm. Providing a max aperture of f1.4 at 50mm, this lens is very fast.
Sigma 50mm F1.4 EX DG HSM is not a weather sealed lens, so you have to be extra careful against rain and dust.