Leica APO-Summicron-SL 50mm F2 ASPH 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 f2 at 50mm, this lens is very fast.
Leica APO-Summicron-SL 50mm F2 ASPH is weather sealed which makes it an ideal lens for outdoor use, especially when coupled with a weather sealed camera body.