Nikon 50mm F1. 4G AF-S Nikkor Lens Description. The Nikon AF-S 50mm f 1. 4G lens is a fast fixed focal-length Nikkor lens that incorporates the built-in Silent Wave Motor SWM enabling smooth & quiet autofocus with Nikon DSLRs including the D40 D40x & D60. The enhanced optical system delivers fantastic image quality minimising both flare & chromatic aberration while the use of a circular aperture diaphragm means out of focus background blur appears more natural. During focusing all the lens groups shift but the front element & filter mount do not rotate & the barrel length does not change making it an ideal lens for close-up photography or when using SB-R200 Wireless Remote Speedlight units. The lens has has two focus modes MA manual-priority autofocus & M manual focus. When mounted on a DX-format SLR the picture angle is equivalent to a focal length of about 75mm in 35mm format.