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Color Perception

Color Perception. Color Perception. Color Spectrum. Red. Violet. 430 THz. 750 THz. 700 nm. 400 nm. Additive colors. The Human Eye. The photosensitive part of the eye is called the retina .

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Color Perception

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  1. Color Perception CS-321Dr. Mark L. Hornick

  2. Color Perception CS-321Dr. Mark L. Hornick

  3. Color Spectrum Red Violet 430 THz 750 THz 700 nm 400 nm

  4. Additive colors CS-321Dr. Mark L. Hornick

  5. CS-321Dr. Mark L. Hornick

  6. The Human Eye • The photosensitive part of the eye is called the retina. • The retina is largely composed of two types of cells, called rods and cones. Only the cones are responsible for color perception. CS-321Dr. Mark L. Hornick

  7. The Fovea CS-321Dr. Mark L. Hornick

  8. 400 nm 700 nm • There are three types of cones, referred to as S, M, and L. They are roughly equivalent to blue, green, and red sensors, respectively. Their peak sensitivities are located at approximately 430nm, 560nm, and 610nm for the "average" observer. • Colorblindness results from a deficiency of one cone type. CS-321Dr. Mark L. Hornick

  9. RGB Color matching functions CS-321Dr. Mark L. Hornick

  10. Color Perception • Different spectra can result in a perceptually identical color sensations called metamers • Color perception results from the simultaneous stimulation of 3 cone types (trichromat) • Our perception of color is also affected by surround effects and adaptation • Different spectral distributions that “look” the same • Infinitely many metamers produce the same perceived color CS-321Dr. Mark L. Hornick

  11. Primary Colors • Set of colors • E.g., phosphor colors • Combined to produce colors • Within a specified gamut • Can’t produce all visible colors • Good enough approximation for most cases CS-321Dr. Mark L. Hornick

  12. CIE • Commission Internationale de l’Éclairage • International Commission on Illumination • 1931 • Color primaries • Imaginary colors • Chromaticity diagram CS-321Dr. Mark L. Hornick

  13. CIE Color Primaries Color-matching functions Mix x,y,z primaries Match any visible color CS-321Dr. Mark L. Hornick

  14. CIE Chromaticity Diagram CS-321Dr. Mark L. Hornick

  15. 520 540 510 560 500 580 600 490 700 480 CIE Diagram Details Spectral colors around curve “Line of purples” White reference (C) SIGGRAPH 1995 Educator’s Slides CS-321Dr. Mark L. Hornick

  16. 520 540 510 560 500 580 600 490 700 480 Color Gamut Line between color points indicates mixing results. Polygon (triangle) connecting primaries delimits gamut. CS-321Dr. Mark L. Hornick

  17. Color Models (1) • RGB: red,green,blue • YIQ: luminance, chrominance • Y: luminance, 4 MHz • I: orange-cyan, 1.5 MHz • Q: green-magenta, 0.6 MHz • CMY: cyan, magenta, yellow • Subtractive primaries (CMYK?) CS-321Dr. Mark L. Hornick

  18. Subtractive colors CS-321Dr. Mark L. Hornick

  19. Color Models (2) • HSV: hue, saturation, value • Hue: “color” • Saturation: purity of color • Value: black to white • HLS: hue, lightness, saturation CS-321Dr. Mark L. Hornick

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