El-Nikkor Enlarging Lenses are made using Nikon optical glass which is corrected for chromatic aberration beyond the visible spectrum into near ultraviolet wavelengths. This means El-Nikkor enlarging lenses can be used for color separation in addition to all other enlarging applications. El-Nikkor lenses are front threaded to accept screw-in accessories and can be used for macro photography when mounted on a bellows.