How to Find Distance Between Two Colors Using Chromaticity

A general C.I.E. chromaticity diagram reveals all the colors perceptible by the human eye. Merriam-Webster defines chromaticity as "the quality of color characterized by its dominant or complementary wavelength and purity taken together." Moreover, the idea of chromaticity comes from a need to identify colors numerically according to their wavelength in the visible spectrum and brightness. In order to find the difference between two colors using chromaticity, you will need to know the color's wavelength and hue. With these values, you can create a coordinate system and find a numerical difference between colors.

Things You'll Need

  • CIE color chart
  • Spectrophotometer
  • Visible spectrum wavelength chart
  • Pencil
  • Paper
  • Calculator
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Instructions

    • 1

      Find the wavelength of the first color. You can find the wavelength either by using a spectrophotometer or by searching the Internet for color wavelength charts. The spectrophotometer or color charts should show wavelengths in nanometers.

    • 2

      Find the X,Y and Z values. The CIE color chart assigns X,Y and Z values to different wavelengths of color. Use the charts to find the specific values for your color.

    • 3

      Use the X,Y and Z values to determine the CIE hue of the color. The CIE hue is composed of three variables known as little x, little y and little z. To find the variables, use the formulas:

      little x = X/(X+Y+Z)

      little y = Y/(X+Y+Z

      little z = Z/(X+Y+Z)

    • 4

      Write down the little x, little y and little z values of the color.

    • 5

      Use the CIE color chart and the equations to find the little x, little y and little z values for the second color.

    • 6

      Create a three-dimensional graph with the little z-axis running vertically, the little x-axis pointing off the page toward you and the little y-axis running horizontally.

    • 7

      Label each of the axes from your graph so the little x, y and z coordinates will fit within the scales.

    • 8

      Plot the points from each of the colors on the graph; this will give you a visual representation of the difference between the two colors.

    • 9

      Subtract each of the coordinates of one color from the matching coordinates of the other color to get the numerical difference.

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