What is color?

The basic definition of color from the Merriam-Webster on-line dictionary is: A phenomenon of light (as red, brown, pink, or gray) or visual perception that enables one to differentiate otherwise identical objects.

The two most important words in this definition are light and visual. Without light and the ability (vision) to see light there is no color. The sun emits electromagnetic radiation across a wide spectrum that includes both visible and invisible wavelengths. In this tutorial we are not concerned with the invisible spectrum, radio waves, gamma waves, etc. but rather the visual spectrum (the wavelengths of light that human vision can perceive).

The human eye is sensitive to light from approximately 380 to 780 nanometers. Light wavelengths are measured in nanometers. Some wavelengths have high energy and short wavelengths (blue/violet side of spectrum) and some low energy and long wavelengths (red/yellow side of spectrum).

The visual spectrum shown here contains all of the colors visible to the human eye. When we see equal amounts of all of these wavelengths we see white light. The absence of all wavelengths or no light would be black.

Please note that the full visual spectrum cannot be reproduced by any capture, display or printing device. They all have limited and differing color gamut's, a term that we will define and explore later in this tutorial.

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