12-30-2015, 04:19 AM
Glass alters color both by absorption, which is not constant w.r.t. wavelength (color) but also by dispersion, where it spreads the colors out.
Dispersion is to fault for both axial color and lateral color.
Marching up to the 80s there were more and more and more glasses available to designers - peaking at about 450 glasses. At that point the EPA went on a bit of a "rampage" trying to eliminate lead and arsenic and the number of glasses available fell to just 20-40. It has rebounded to around 140 total but is still a far cry from what it used to be.
The new glasses are mildly different w.r.t. their absorption profiles, but I am extremely doubtful that he knew this.
The idea of "color-matching" lenses is all done with the coatings. The glass choices are not restricted for that beyond basic checks to ensure the high transmission bandwidth covers all of the visible range.
The higher contrast the lens, the more "pure" the colors. The less axial and lateral, but especially axial, color the lens has the more "pure" the colors. Older lenses had less contrast because they were not as well corrected and assembled, the result would be "softer" and more "pastel" like colors.
However the color fidelity of consumer lenses has never been higher than it is today.
Dispersion is to fault for both axial color and lateral color.
Marching up to the 80s there were more and more and more glasses available to designers - peaking at about 450 glasses. At that point the EPA went on a bit of a "rampage" trying to eliminate lead and arsenic and the number of glasses available fell to just 20-40. It has rebounded to around 140 total but is still a far cry from what it used to be.
The new glasses are mildly different w.r.t. their absorption profiles, but I am extremely doubtful that he knew this.
The idea of "color-matching" lenses is all done with the coatings. The glass choices are not restricted for that beyond basic checks to ensure the high transmission bandwidth covers all of the visible range.
The higher contrast the lens, the more "pure" the colors. The less axial and lateral, but especially axial, color the lens has the more "pure" the colors. Older lenses had less contrast because they were not as well corrected and assembled, the result would be "softer" and more "pastel" like colors.
However the color fidelity of consumer lenses has never been higher than it is today.