Introduction to Color
Color is the wavelength of the light the human eye receives when we look at an object. In theory, the color spectrum is infinite. Humans, however, can see only a small portion of this spectrumthe portion that goes from the red edge of infrared light (the longest wavelength) to the blue edge of ultraviolet light (the shortest wavelength). This continuous spectrum is called the visible spectrum.
White light is a combination of all colors. The spectrum of white light is continuous and goes from ultraviolet to infrared in a smooth transition. You can represent a good approximation of white light by selecting a few reference colors and weighting them appropriately. The most common way to represent white light is to use three reference components, such as red, green, and blue (RGB) primaries. You can simulate most colors of the visible spectrum using these primaries. For example, video projectors use red, green, and blue light generators, and an RGB camera uses red, green, and blue sensors.
The perception of a color depends on many factors:
- Hue—The perceived dominant color. Hue depends directly on the wavelength of a color.
- Saturation—The amount of white light present in a color. Pastels typically have a low saturation while very rich colors have a high saturation. For example, pink typically has a red hue but has a low saturation.
- Luminance—The brightness information in the video picture. The luminance signal amplitude varies in proportion to the brightness of the video signal and corresponds exactly to the monochrome picture.