Thule MED9

Value expresses the lightness or darkness of a color, rather than its temperature or hue. It can be evaluated using a scale that ranges from the darkest to the lightest values. In our proposed scale, 1 represents white, the lightest value, while 9 represents black, the darkest.
Imagine taking a photograph of a color and converting it to black and white. This allows you to perceive the color’s value—its relative lightness or darkness.