The voigtlander 40mm f2 color ultron sl ii lens with nikon fit is an ultra compact manual focus prime lens ideal for use on nikon full frame dslrs for everyday travel photography when used on a dslr with an aps c size sensor the focal length is roughly 60mm the lens incorporates a cpu central processing unit to support metering and exposure information while the state of the art optical design with multi coated optics and two aspherical elements ensures sharp images throughout with minima