Color - (Lightness|Value|Tone) (White, Gray, Black scale)

About

Lightness, also known as value or tone, is a property (coordinate) placed on a linear scale where:

• White is the highest possible value (the lightest)
• Black is the lowest value (the darkest)
• Gray is the a medium value. The midpoint between black and white, neither dark nor light.

Some colors are naturally:

• light like yellow (high lightness, high value)
• darker, like violet (low lightness, low value)

and can therefore be projected on the greyscale.

Name

Various color models have an explicit term for this property.

• The Munsell color model uses the term value
• The HSL color model and Lab color space use the term lightness.
• The HSV model uses the term value a little differently: a color with a low value is nearly black, but one with a high value is the pure, fully saturated color.

Colorspace

Lightness may be used in colorspace as coordinate. Example with HSL.

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Operation

Tint (Increase) vs Shade (decrease)

In subtractive color (i.e. paints), lightness value changes can be achieved by adding black or white to the color.

• tint: Adding white paint will make any pigment lighter.
• shade: Adding black paint will make most pigments darker, but will cause yellow paint to shift in hue to green.

Calculation

From Rgb

from a rgb colorspace

$max = max($red, $green, $blue);
$min = min($red, $green, $blue);
$lightness = ($max + $min) / 2;

Documentation / Reference

• wiki/Lightness