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

measures how much light is reflected at each wavelength over the visible spectrum.
Notice how the ink tends to reflect more light in the short-wavelength portion
of the spectrum. This is expected, as the respective colors at those wavelengths
are from violets and blues to blue-greens. The blue ink also absorbs much of the
orange and red regions of the spectrum, as the reflectivity in these regions is low.
Figure 3.4: An example of subtractive color mixture. Adapted
from [SB02].
Panel B shows the reflectance spectrum for a yellow ink, which tends to reflect
wavelengths longer than 500nm and absorbs light in the violet and blue regions.
When these two inks are mixed together, the resulting ink reflects only where both
inks reflect appreciable amounts of light. The remaining area is in the middle of
the spectrum, or green (which is what we expect).
Combining the three primary subtractive colors: cyan, magenta and yellow,
one obtains a gamut of available colors. The absence of all of these colors leaves
white, while the full presence of all three combines to make black. Other than
dyes, other materials behave as subtractive <strong>colorants</strong>, such as inks, colored filters
and photographic emulsions.
Color can also be produced via additive color mixing. Though it is rare in
nature, additive color is essential in display monitors such as television and com-
puter screens. The system involves light emitted directly from an illuminant (not
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