Color, How We See Light

this was originally published on my webpage 3 years ago, enjoy =)

Introduction

Light is a form of radiant electromagnetic energy which, for our purposes, travels as a wave. While this is not exactly correct it is all we need to concern ourselves with to understand color.
The color we see is dependant on the wave length of the light that reaches our eyes.
Visible light is a range of electromagnetic wave lengths that the human eye is sensitive to. The range is about 400 to 700 nm (nanometers). Below 400nm we find ultraviolet radiation, X-rays and Gamma-rays. Above 700nm we encounter infrared radiation, radar, television, and radio.
White light is a combination of all visible wave lengths. Black is an absence of light.

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Bending the Light
If you take a beam of white light and shine it into a prism the prism will bend the light. The shorter wave lenths will bend more than the longer wave lengths thus the white light will be spread out into a visible spectrum.


By placeing filters in the path of the light we will only see the light waves that are passed by the filter. A red filter will only pass red light. Green passes green. Blue passes blue.

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The Additive Property
The next step in our understanding of color is called the additive property. Imagine if you would the next image being created by three projectors projecting white light. Projector 1 has a red filter, 2 has a green filter and 3 has a blue filter on it. When the lights are arranged so they overlap the colors will blend into new colors. Red and green blend to create yellow, green and blue create cyan, blue and red blend to create magenta.

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Subtractive Property
Now again we are going to imagine the three images below are a white light with red, green, and blue filters on it and we are going to hold a different color filter over the red, green, blue.


Much like Red Green and Blue light can be added we can use Yellow, Cyan and Magenta light subtractivly.


Think about it like this, white is all the light together. Printers subtract colors from the white paper using yellow, cyan, and magenta pigments.
We create images on our black (lightless) computer screens by adding red, green and blue light.