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Perceiving Color
It has been estimated that the human visual system can detect and discriminate among 7 million
color variations (Geldard, 1972), [6] but these variations are all created by the combinations of the
three primary colors: red, green, and blue. The shade of a color, known as hue, is conveyed by
the wavelength of the light that enters the eye (we see shorter wavelengths as more blue and
longer wavelengths as more red), and we detect brightness from the intensity or height of the
wave (bigger or more intense waves are perceived as brighter).
Figure 4.14 Low- and High-Frequency Sine Waves and Low- and High-Intensity Sine Waves and Their
Corresponding Colors