AF DC-Nikkor 105mm f/2D and AF DC-Nikkor 135mm f/2D. ED — "Extra-low Dispersion" glass incorporated to reduce chromaticaberration. Lenses using ED elements
being very good while many inexpensive single element lenses exhibit chromaticaberration and reduced sharpness of the resulting image. This method works with
Zeiss Planar design of 1896 to correct for chromaticaberration. It was the original six element symmetric f/4.5 double Gauss lens.: 121–122 Horace William