Technical camera users will soon have available what is one of the most highly corrected and high performing lenses ever made available commercially— the Caldwell Photographic 120mm f/4.5 Macro UV-IR Apochromat. The new lens is designed by Brian Caldwell, optical designer of the Coastal Optics 60mm f/4 UV-VIS-IR APO macro.
The lens design utilizes 9 elements in 7 groups. Six of them are special low dispersion (ED) glass, and the rear element is aspheric. The lens focuses to 1:1 on medium format, with a 70mm image circle wide open. Makes me want to run out and get a view camera and digital back!
The lens is so highly corrected that focusing can be done in visible light with no correction whatsoever for ultraviolet or infrared from 320nm through 1100nm. This is critical for the intended scientific, multi-spectral and forensic purposes. That same correction means that there is absolutely no violet fringing (purple fringing eg axial chromatic aberration). My experience with the Coastal Optics 60/4 tells me that such correction results in a uniquely transparent look to the images, with stunning color rendition.
The MTF chart is extraordinary. The line pairs charted include 10/20/40 and 80 (eighty) line pairs per mm. What is astonishing about the 80 line pairs/mm lines is that they are better than many lenses can show at 40 line pairs/mm. You’re not likely to see higher performance from any lens. It’s also an f/4.5 lens, which makes it more flexible than some of the f/5.6 alternatives.