brightnessHue, saturation, andbrightness are aspects of color in the red, green, and blue ( RGB ) scheme. These terms are most often used in reference to the color of each pixel in a cathode ray tube ( cathode ray tube )display. All possible colors can be specified according to hue,saturation, andbrightness (also called brilliance ), just as colors can berepresented in termsof the R, G, and B components. Most sources of visible light contain energy over a band of wavelength . Hue is the wavelength within the visible-light spectrum at which the energy output from a source is greatest. This is shown as the peak of the curves in the accompanying graph of intensity versus wavelength. In this example, all three colors have the same hue, with a wavelength slightly longer than 500 nanometers, in theyellow-green portion of the spectrum. 
Saturation is an expression for the relative bandwidth ofthe visible output from a light source. In the diagram, the saturation isrepresented by thesteepness of the slopes of the curves. Here, the redcurverepresents acolor having low saturation, the green curve represents a color havinggreatersaturation,and the blue curve represents a color with fairly high saturation. Assaturationincreases, colors appear more "pure." As saturationdecreases, colorsappear more "washed-out." Brightness is a relative expression of the intensity of theenergy outputof a visible light source. It can be expressed as a total energyvalue(differentfor each of the curves in the diagram), or as the amplitude at thewavelengthwhere theintensity is greatest (identical for all three curves). In the RGBcolormodel, theamplitudes of red, green, and blue for a particular color can each rangefrom0 to 100percent of full brilliance. These levels are represented by the rangeofdecimalnumbers from 0 to 255, or hexadecimal numbers from 00 to FF.
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| Last updated on:
Apr 05, 2005 |
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