The 135mm f/2.8 Smooth Transition Focus Lens from Sony is a manual focus prime lens that uses Sony's Smooth Trans Focus (STF) technology for a very unique effect on defocused light sources, changing the way defocused areas appear depending on how it is adjusted. The lens is constructed of 8 elements in 6 groups which all help to deliver sharp, clear photos. It has a minimum focusing distance of 2.9' and a front-end filter diameter of 72mm.