1 / 20

COLOR PERCEPTION

COLOR PERCEPTION. Physical and Psychological Properties Theories Trichromatic Theory Opponent Process Theory Color Deficiencies Color and Lightness Constancies. Properties of Color. Trichromatic Theory.

francis-vaughan
Télécharger la présentation

COLOR PERCEPTION

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. COLOR PERCEPTION • Physical and Psychological Properties • Theories • Trichromatic Theory • Opponent Process Theory • Color Deficiencies • Color and Lightness Constancies

  2. Properties of Color

  3. Trichromatic Theory • All colors are perceived as combinations of three primaries: red, green, and blue • This refers to additive mixing, in which color combining happens in the visual system (subtractive mixing is when pigments or dyes are mixed)

  4. Trichromatic Theory • People with normal color vision need three primaries to match any color • Color TV is based on this principle

  5. Trichromatic Theory • Three types of cone cells with three types of photopigments: • Short (419 nm) • Medium (531 nm) • Long (558 nm)

  6. Opponent Process Theory • All colors are perceived as a combination of opponent pairs of colors: • red-green • blue-yellow

  7. Opponent Process Theory • We don’t see colors that combine opponents (e.g., reddish green) • Negative color afterimages • Simultaneous color contrast - change in appearance of a color caused by surrounding color

  8. Opponent Process Theory • Opponent neurons in LGN: • B+Y- • Y+B- • R+G- • G+R-

  9. Which Theory is Correct ? • Both! • Trichromatic Theory describes processing of cones • Opponent Process Theory describes processing at higher levels in the visual system

  10. S L M cones bipolars R+G- B+Y- ganglions

  11. Blue light S L M R+G- B+Y- “blue”

  12. Yellow light S M L R+G- B+Y- “yellow”

  13. Red light S M L R+G- B+Y- “red”

  14. Green light S M L R+G- B+Y- “green”

  15. Color Vision Deficiencies • cerebral achromatopsia - no color vision; due to damage in secondary visual cortex • monochromat - no color vision; due to abnormal or missing photopigments

  16. Color Vision Deficiencies • dichromat - can match all colors using only two primaries • protanopia - no L pigment (red-green loss) • deuteranopia - no M pigment (red-green loss) • tritanopia - no S pigment (blue-yellow loss)

  17. Color Vision Deficiencies • anomalous trichromat – three cone systems, but two of them are too close together • most common color vision problem

  18. Color Constancy • We perceive the hue of an object as constant even when the wavelength illuminating it changes • May be due to comparing reflectance patterns from various objects

  19. Lightness and Brightness • lightness refers to perception of the intensity of an achromatic color • brightness refers to perception of the intensity of chromatic colors

  20. Lightness Constancy • Perception of an object with an achromatic color is the same even when the amount of light reflected changes • Ratio principle: compare amount of light reflected from other objects to perceive lightness of an object

More Related