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Lecture 7 - Colour Vision

Lecture 7 - Colour Vision. Physical Basis for Colour Perception Individual Differences in Colour Perception Physiological Basis for Colour Perception Trichromatic Theory Opponent Process Theory Colour Deficiencies. Colour Vision. Physical Basis for Colour Perception

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Lecture 7 - Colour Vision

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  1. Lecture 7 - Colour Vision • Physical Basis for Colour Perception • Individual Differences in Colour Perception • Physiological Basis for Colour Perception • Trichromatic Theory • Opponent Process Theory • Colour Deficiencies PSY 280 - Hamstra

  2. Colour Vision • Physical Basis for Colour Perception • Individual Differences in Colour Perception • Physiological Basis for Colour Perception • Trichromatic Theory • Opponent Process Theory • Colour Deficiencies PSY 280 - Hamstra

  3. Physical Basis for Colour Perception • Newton’s prism experiments • white light composed of all frequencies • spectral reflectance function • refraction, absorption & reflection • colour mixing • subtractive (pigments & filters) • additive (projection) PSY 280 - Hamstra

  4. Colour Vision • Physical Basis for Colour Perception • Individual Differences in Colour Perception • Physiological Basis for Colour Perception • Trichromatic Theory • Opponent Process Theory • Colour Deficiencies PSY 280 - Hamstra

  5. Individual Differences in Colour Perception • complementary colours • Hering's hue circle • 4 unitary hues • 2 achromatic colours • colour measurement standards • CIE chromaticity diagram PSY 280 - Hamstra

  6. Colour Vision • Physical Basis for Colour Perception • Individual Differences in Colour Perception • Physiological Basis for Colour Perception • Trichromatic Theory • Opponent Process Theory • Colour Deficiencies PSY 280 - Hamstra

  7. Physiological Basis for Colour Perception • spectral reflectance function • colour constancy • retinal distribution of cones • resolution limit • additive colour mixing: • e.g. pointillist paintings (Suerat), colour TV PSY 280 - Hamstra

  8. Colour Vision • Physical Basis for Colour Perception • Individual Differences in Colour Perception • Physiological Basis for Colour Perception • Trichromatic Theory • Opponent Process Theory • Colour Deficiencies PSY 280 - Hamstra

  9. Trichromatic Theory • spectral sensitivity curve • 3 types of cones • metameric match and the principle of univariance • the problems with one- and two-pigment systems • colour experience determined by relative activity of 3 cone types PSY 280 - Hamstra

  10. Key Point • variation in wavelength will not, by itself, lead to a perception of change in colour • i.e. 1-pigment system will only see differences in brightness • need at least 2 systems to signal change in ratio of responses • (remember: everything is signaled by neural responses) PSY 280 - Hamstra

  11. Key Point • “colour” is simply the name we give to the subjective experience that corresponds to our ability to distinguish between different wavelengths of light • it depends entirely on the eye that is looking PSY 280 - Hamstra

  12. Colour Vision • Physical Basis for Colour Perception • Individual Differences in Colour Perception • Physiological Basis for Colour Perception • Trichromatic Theory • Opponent Process Theory • Colour Deficiencies PSY 280 - Hamstra

  13. Opponent Process Theory • pairs of colours, opposing each other • 3 fundamental colour processes: • one achromatic: B & W • two chromatic: R-G, B-Y • evidence for opponent processes: • perceptual impossibilities • colour contrast • afterimages • LGN cell responses PSY 280 - Hamstra

  14. Colour Vision • Physical Basis for Colour Perception • Individual Differences in Colour Perception • Physiological Basis for Colour Perception • Trichromatic Theory • Opponent Process Theory • Colour Deficiencies PSY 280 - Hamstra

  15. Colour Deficiencies • dichromacies: • protonopia - missing L type • deuteranopia - missing M type • tritanopia - missing S type • equiluminant chromatic stimuli • Ishihara plates PSY 280 - Hamstra

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