pigmented colorants: dependence on media and time - Cornell ...

Figure 3.3: Setup for Newton’s basic experiment. In this case, after
white light was decomposed, the resulting green light is selectively allowed
to pass through the second aperture and the second prism, yet
the light remains green. Hence, Newton would deem the green light
pure. Adapted from [SB02].
subtractive color mixing, since the primaries absorb (or subtract) a portion of the
incident light, keeping that portion from your eye. The light that is not absorbed
is reflected and visible to the eye. For instance, inks are a common example of a
subtractive colorant. If white light strikes ink that absorbs all spectra except long
wavelengths, it will appear red. Multiple inks superposed will absorb the other’s
reflecting spectra. The resulting color from the ink mixture will be comprised only
of reflected light that is not absorbed by any of the inks. Thus, the combination of
several subtractive <strong>colorants</strong> yields a mixture whose total reflectance is the product
of the constituents:
C =
i
Hence, multiplicative mixing would be a more appropriate name, but the term
subtractive color has stuck. The term subtractive mixing possibly originates from
the different components absorbing the other’s contributing spectra.
To illustrate the system, consider the curve in panel A of Figure 3.4 which
shows the reflectance spectrum of a typical blue ink. A graph of spectral reflectance
Ci
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