Technical Issues - RGB Comparator

Does a 2 nm shift affect perceived color? What about 10 nm, as shown here? Can you replace filter glass with a dichroic coating? Referring to the highpass design below, will changing (.25L .25H)8 to (.25L .25H)3 affect color perception?

The DESIGN Interactor RGB Comparator (2.61.0200) helps users compare the color of an imported spectrum with the calculated spectrum (circle).

Set the Interactor Mode to Compare or Difference and paste a spectrum or open a measured curve. The curve must include 380-780 x1 or x5 nm. Click Evaluate.. RGB Comparator. Although the same colors are shown in the status bar, the Comparator makes differences easier to see. The screen shots below indicate the procedure step-by-step. Note that RGB simulation assumes D65 illuminant.


In Design Mode we see both reflected and transmitted colors.


Compare or Difference Mode gives reflected or transmitted color.


Click Spectra...Copy followed by Spectra...Paste to simulate
an imported spectrum, here overlapping the current spectrum.
There are now two identical color bars.


Changing Design Wavelength from 460 to 470 nm reveals two curves.
The color bar for the imported spectrum (blue line) is at the left.


Click Evaluate...RGB Interactor to display colors in an exploded format.

This capability was inspired by stumbling upon Edmund Optics 45 Reflective Dichroic Color Filters and finding that Coating Tolerances are 15 nm. (Possibly a mistake; 5 nm seems more reasonable.)

Responding to the above, a user pointed out the difficulty in comparing RGB colors for AR coatings. This is an issue in products such as ophthalmic lenses and camera filters where cosmetic appearance is important. While the eye distinguishes dim reflected colors, the RGB representation does not, as shown below:


Impossible to distinguish nearly black RGB colors

Click Evaluate...RGB Boost (DESIGN 2.61.0201). Specifying Boost > 1 enhances reflected colors by scaling CIE tristimulus values. Boost is disabled by setting the value to 1. Note the yellow warning message. Boost applies only to reflection. This is a heuristic method and not an accurate representation.


RGB Boost provides an indication of reflected color

Other color-related pages: Excel Color Grid, Reverse-Engineering by Color Matching, Color Measurements with Diode-Array Spectrometers.