There are three points of interest on the line representing the color of the mix. They are: The "White Point" at position W, The color of the mix "M", at position M, and the "Saturation Point" at point S on the chromacity curve. The distance between W and S represents 100% saturation of the color, while the distance between W and M is called the color's "Excitation Purity" and is expressed as a percentage of the color's maximum saturation.

Here I have used simple Geometry to calculate these distances.

On the diagram to the right the distances are determined from the diagram's "Cartesian Coordinates". Greater asccuracy can be achieved by magnifying the Scale as in the example found by clicking here.

|SW| = [(0.146)2 + (0.219)2]1/2 = 0.263 units

and the distance from W to M will be:

|MW| = [(0.062)2 + (0.092)2]1/2 = 0.111 units

The Color's Excitation Purity will be: 0.111 / 0.263 X 100 = 42.2%, and the color's Luminous Transmittance will be: 100 - 42.2 = 57.8%. Reset.