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| Color Models |
| The HSB/HLS Color Model |
HSB/HLS are two variations of a very basic color model for defining colors in desktop graphics programs that closely matches the way we perceive color. This model is somewhat analogous to Munsell's system of hue, value, and chroma in that it uses three similar axes to define a color. In HSB, these are hue, saturation, and brightness; in HLS, they are defined by hue, lightness, and saturation.
Hue defines the color itself, for example, red in distinction to blue or yellow. The values for the hue axis run from 0–360° beginning and ending with red and running through green, blue and all intermediary colors like greenish-blue, orange, purple, etc. In this respect, HLS is very similar to Munsell's color wheel. Although Munsell used a different method for indicating hue, both arrange the colors in a circular pattern and progress them through compass points.
Saturation indicates the degree to which the hue differs from a neutral gray. The values run from 0%, which is no color saturation, to 100%, which is the fullest saturation of a given hue at a given percentage of illumination.
This is similar to Munsell's chroma.
Lightness indicates the level of illumination. The values run as percentages; 0% appears black (no light) while 100% is full illumination, which washes out the color (it appears white). In this respect, the lightness axis is similar to Munsell's value axis. Colors at percentages less than 50% appear darker while colors at greater than 50% appear lighter.
A color solid (i.e., a three-dimensional representation) of the HLS model is not exactly cylindrical since the area truncates towards the two ends of the lightness axis and is widest in the middle range. Thus it forms an ellipsoid:
HLS is commonly encountered in one form or another in many computer graphics programs. One common example is Apple's HLS wheel:
By specifying the hue degree and saturation percentage and using the slider bar to control the lightness, you can create any of millions of colors.
HLS is implemented under other names as well: HSB (hue, saturation, and brightness) is common, as is LCH (lightness, chroma, and hue). The values, regardless of what they're called, are very similar.
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