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Importance of Color

Importance of Color. Painters first used charcoal Early artists used ochre to add red Colors are not always the same from culture to culture. Blackbody Radiators. A theoretical model of how objects emit radiation based on temperature Examples Incandescent light 2854K

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Importance of Color

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  1. Importance of Color • Painters first used charcoal • Early artists used ochre to add red • Colors are not always the same from culture to culture

  2. Blackbody Radiators • A theoretical model of how objects emit radiation based on temperature • Examples • Incandescent light 2854K • Direct sunlight 4874K

  3. Emotional Response to Color • Temperature is associated with colors • Blue is cold • Red is warm • Depends on overall scene illumination

  4. Thomas Young • English Physician • 1773-1829 • Every color can be matched by adding three primaries

  5. Hermann Helmholtz • German Scientist • 1821-1894 • Verified Young's theory by identifying three types of receptors in the eye in 1852-3 • Invented opthalmoscope

  6. Retinal Structure

  7. Color Vision • Each cone type is sensitive to a different range • Research indicates we can see about 10 million colors • How can one color be distinguished from another? • How are colors specified?

  8. Color Vision • Depends on relative stimulation of photoreceptors • Depends on wavelength • Monomers • Same colors • Different spectra • Color depends on surrounding colors

  9. Color Deficiency • About 10% have some deficiency • 9% men • 1% women • Most missing red or green cones • Red and green percieved as brown • Monochromats have only rods • Dichromats have 2 of the three cones • Low light vision is not affected • Care needs to be taken when creating visual materials for others • Web pages • Brochures • Design in black and white, then add color

  10. Color Blindness • Protanopia • No red cones • Red, orange, and yellow are shifted toward green • Violet is shifted towards blue • severe cases • traffic lights are black • Purple flowers are blue • Problems in extreme lighting conditions

  11. Color Blindness • Deutanopia • No green cones • Green, yellow, and orange are shifted toward red • Poor discrimination of blues

  12. Color Blindness • Tritanopia • No blue cones

  13. Ishihara Tests

  14. Quantifying Color • CIE • CommisionInternationaled'Eclairage • began work in 1931 • First chart in 1947

  15. CIE Chart • Revised in 1976 • Spectral colors (pure tones) are around perimeter curve • Purple line is not • Neutral color point • Complementary colors • Primary hue

  16. CIE Chart

  17. Color Gamut • Only a small subset of possible perceivable colors can be reproduced • Fall into convex hull of primaries • Two primaries results in a line • Three primaries results in a triangle

  18. RGB Color Model • Additive colors • Three primaries • Red • Green • Blue • Roughly match the sensitivities of cones • Used in digital images • Used in emissive color displays

  19. CYMK Color Model • Subtractive color model • Starts with white • Reduces reflected light • Three primaries • Cyan • Yellow • Magenta • Black (key) is used to reduce brightness without changing the hue

  20. CYMK Color Model

  21. Complementary colors • Opposites • Enhance one another because of optimal color contrast

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