Graphics Reference
In-Depth Information
Color
Strictly speaking, the rays are not
colored.
Optics,
Isaac Newton
Most people are able to sense
color
—it's the sensation that arises when our eyes
are presented with different spectral mixes of light. Light with a wavelength of
near 400 nanometers makes most people experience the sensation “blue,” while
light with a wavelength near 700 nm causes the sensation “red.” We describe color
as a
sensation
because that's what it is. It's tempting to say that the light arriving
at our eyes is colored, and we're just detecting that property, but this misses many
essential characteristics of the perceptual process; perhaps the most significant
one is this: Two very different mixes of light of different frequencies can generate
the same perception of color (i.e., we may say “Those two lights are the same
color green”). Thus, our notion of color, which we use to distinguish among lights
of different wavelengths, is insufficient to distinguish among
mixtures
of lights
at different wavelengths. It's therefore worth distinguishing between the physical
phenomenon (“This light consists of a certain mixture of wavelengths”) and the
perceptual one (“This light looks lime green to me”). Furthermore, our observation
of the same spectral mix may cause different perceptions at different times or
different intensities.
As you read this chapter, you should keep the following high-level facts in
mind.
• Color is a perceptual phenomenon; spectral distributions are physical
phenomena.
• Everything you learned about red, green, and blue in elementary school
was a simplification.
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