Scales for Measuring Colour:

There are two important scales for measuring colour. These are:

•      Munsell Scale

•      CIE colour system

Munsell Scale:

In 1905, artist Albert H. Munsell originated a color ordering system — or color scale — which is still used today. The Munsell System of Color Notation is significant from a historical perspective because it’s based on human perception. Moreover, it was devised before instrumentation was available for measuring and specifying color. This system assigned numerical value to the three properties of the colour-Hue, Chroma and value. The Munsell color system match colors to a set of standard samples. The Munsell system divides hue into 100 equal divisions around a color circle and circle is distorted by assigning a unit of radial distance to each perceptable difference in saturation (called units of chroma). Since there are more perceptable differences for some hues, the figure will bulge outward to 18 values for some hues compared to only 10 for another. Perpendicular to the plane formed by hue and saturation is the brightness scale divided into a scale of "value" from 0 (black) to 10 (white). A point in the color space so defined is specified by hue, value, and chroma in the form H V/C.

The MUNSELL system is a collection of color samples for comparison, with adjacent samples based upon equal perceived differences in color.

Munsell saw that full chroma for individual hues might be achieved at very different places in the color sphere. For example, the fullest chroma for hue 5RP (red-purple) is achieved at 5/26.

Another color such as 10YR (yellowish yellow-red) has a much shorter chroma axis and reaches fullest chroma at 7/10 and 6/10: