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Working with Color
Chapter 5
The properties of color
The physics
of color
This chapter introduces concepts that are basic to color theory. You will
encounter some of these concepts (such as hue, saturation, and
brightness) when you work with color in applications; others provide useful
background information. Color is a complex topic, so consider this a starting
point for experimentation and further research.
What we call "color" is really a perceptual ability unique to humans and a
small number of animal species. Color theory is an attempt to systematize
the properties of color perception, which by nature is relative and
changeable. A color appears different depending on the other colors around
it, and individuals vary in their abilities to perceive color.
The human eye can see electromagnetic radiation at wavelengths between
400 nanometers (purplish blue) and 700 nanometers (red). This range is
called the visible spectrum of light. We see pure spectral light as intensely
saturated or pure colors. Sunlight at midday, which we perceive as white or
neutral light, is composed of light from across the visible spectrum in more
or less equal proportions. Shining sunlight through a prism separates it into
its spectral components, resulting in the familiar rainbow of colors.
Like the sun, most light sources we encounter in our daily environment emit
a mixture of many light wavelengths, although the particular distribution of
wavelengths can vary considerably. Light from a tungsten light bulb, for
example, contains much less blue light than sunlight. Tungsten light
appears white to the human eye which, up to a point, can adjust to the
different light sources. However, color objects appear different under
tungsten light than they do under sunlight because of the different spectral
makeup of the two light sources.
The mixture of light wavelengths emitted by a light source is reflected
selectively by different objects. Different mixtures of reflected light appear
as different colors. Some of these mixtures appear as relatively saturated
colors, but most appear to us as grays or impure hues of a color.
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