Updated: 9/10/2019

Return to the Chromaticity Diagram


Basic Challenges

  1. (x,y,I) Space Completeness: Demonstrate that you can vary the relative eye cone response values (x,y) and the intensity of the maximal pixel emitter (I) to produce any color that can be displayed on a W3C-compatible screen.
  2. The Color Brown: Demonstrate how various shades of brown are produced on the Chromaticity Diagram.
  3. The Color White: Demonstrate that the color white is produced at any pixel by setting equal emissions from the pixel's three emitters.
  4. Color Shades: Describe how to determine the Diagram region representing shades of light blue and demonstrate doing it.
  5. Diagram Non-linearity I: Demonstrate that at any point on the diagram that is on a line between two vertices, the contribution of the third-vertex emitter is zero.
  6. Diagram Non-linearity II: Demonstrate that, at the visual midpoint between two vertices, the contributions of the emitters at those two vertices are not equal.
  7. Unique RGB Components: Explain why, at any particular (x,y,I) position within the RGB boundary, there is a unique set of RGB contributions.
  8. No Photon Color can be a mixture: Use the Diagram to explain why no photon color can be a mixture of photon colors.
  9. All non-photon colors are mixtures: Use the Diagram to explain why every non-photon color must be a mixture of photon colors.
  10. No Photon Colors on the Screen: Use the Diagram to explain why no photon color can be shown on a W3C-compatible screen.
  11. Non-Unique Photon Components: Explain why there are an infinite number of different photon combinations (spectra) that will produce any given color inside the Chromaticity Diagram boundary made by the visible-photon locus and the straight line connecting the two limits of the locus.

Advanced Challenges

  1. A Color's Spectrum: If a spectroscope is available show that it can be used to see the mixture of photons which are being used to produce any particular light-beam color.
  2. Explain that the colors in the Chromaticity Diagram refer to the colors of light beams and not to the "colors of objects" (the colors of light beams coming from objects).
  3. Describe the journey of a photon from an emitter in the interior of the sun to an absorber in the interior of the eye.
  4. Describe what is known about the journey of a nerve signal from a photon-absorber pixel in the interior of the eye to a consciousness of the pixel color in the brain.
  5. Describe how the "color of an object" (the color of a light beam coming from an object) can be calculated from the spectrum of the light incident upon the object plus the spectral reflectivity data for that object's surface.

© Project Physnet, 2019; Contact: Peter Signell, signell@msu.edu