- a light source
- an object
- a viewer
Light from the sun or another light source strikes objects around us, is reflected and modified by the objects, then reaches the receptors in our eyes and is interpreted by our brains into something we call color. Since color only exists in our minds, explaining the physical aspects of color is just part of the story. The way objects appear to us and the judgements we make about color are determined by a combination of many factors. Some of these factors are easy to measure and some are not. Individual perceptual differences, eye fatigue and mood of the viewer are as important to a discussion about color as are the properties of light sources and objects. Color as perceived by the human eye cannot be simulated by any instrument, nor can it be reproduced by any printing process.
Light is essential for vision. Light causes color. Without light color would not exist. Light that appears white to us, such as light from the sun, is actually composed of many colors. Each color has its own measurable wavelength or combination of wavelengths. (Light travels in wvese much like waves produced by dropping a pebble in a pond, except light waves are extremely small.) The wavelengths of light are not colored, but produced the sensation of color. Light is a form of energy. All wavelengths of light are part of the electromagnetic energy spectrum. The spectrum is a continuous sequence of energy waves that vary in lengths from short to long. Visible light – the wavelengths our eyes can detect – is a small portion of the entire spectrum. At one end of the visible spectrum are the short wavelengths of light was perceived as blue. At the other end of the visible spectrum are the longer wavelengths of light we perceive as red. All the other color we can see in nature are found somewhere along the spectrum between blue and red. Beyond the limits at each end of the visible spectrum are the short wavelengths of ultraviolet light and X-rays and the long wavelengths of infrared radiation and radio waves which are not visible to the human eye.
We can separate a beam of white light into its component colors by passing it through a glass prism which causes the light beam to bend. Each wavelength, or color, bends at a slightly different angle which separates the white light into an array of colors. When the sun comes out after a rainstorm, water droplets in the air can act as prisms and display the arc of colors in the sky we see as a rainbow.
the visible portion of the spectrum is divided into thirds, the predominant colors are blue, green and red. These are primary colors of light. Visible colors can be arranged in a circle, commonly known as the color wheel. Blue, green and red form a triangle on the color wheel. In between the primary colors are the secondary colors, cyan, magenta and yellow which form another triangle.