| 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. |
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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.
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