# Hue, Saturation, and Value Color Model

The HSV (Hue, Saturation, and Value) color model is more intuitive than the RGB color model. The user specifies a color (hue) and then adds white or black. There are 3 color parameters: Hue, Saturation, and Value. Changing the saturation parameter corresponds to adding or subtracting white and changing the value parameter corresponds to adding or subtracting black.

The 3D representation of the HSV model is derived from the RGB mode cube. If we look at the RGB cube along the gray diagonal we can see a hexagon that is the HSV hexcone. The hue is given by the angle about the vertical axis with red at 0°, yellow at 60°, green at 120°, cyan at 180°, blue at 240°, and magenta at 300°. Note that the complementary colors are 180° apart.

The saturation varies between 0.0 <= s <=1.0 and is the ratio of purity of a related hue to its maximum purity at s="1." at s equals 0 is the gray scale, that is the diagonal of the RGB cube corresponds to v of the HSV hexcone. notice the complementary colors( red + cyan, blue + yellow, green + magenta ) are diagonally opposite.

So to choose a color we do the following:
1. select pure hue (specifies H and sets S = V = 1)

For Example: pure blue H = 240°, S = V = 1
dark blue H = 240°, S = 1, V = 0.40
light blue H = 240°, S = .3, V = 1.0

Intuitive color concepts

Artists start with a "pure color or hue", then add black pigment to produce different shades. The more black pigment the darker the shade. They add white pigment and get different tints. Adding both black and white pigments gives different tones. If we look at the cross-section of the hexcone we can see the analogy with the artists model.

The human eye can distinguish about 128 different hues, 130 different tints (saturation levels), and from 16 (blue part of spectrum) to 23 (yellow part of spectrum) different shades. So we can distinguish about 128 X 130 X 23 = 380,000 colors.

Main Color page