1. COLOR VISION
© Stephen E. Palmer, 2002

2. COLOR VISION “The Color Story” is a prototype for Cognitive Science
Contributions from:
Physics (Newton)
Philosophy (Locke)
Art (Munsell)
Psychophysics (Maxwell)
Physiology (De Valois)
Cognitive Psychology (Rosch)
Neurology (Zeki)
Linguistics (Lakoff)
Cognitive Anthropology (Berlin & Kay)
Computer Science (Zadeh)
© Stephen E. Palmer, 2002

3. COLOR VISION “The Color Story” is a prototype for Cognitive Science
Contributions from: * Berkeley faculty
Physics (Newton)
Philosophy (Locke)
Art (Munsell)
Psychophysics (Maxwell)
Physiology (De Valois)
Cognitive Psychology (Rosch)
Neurology (Zeki)
Linguistics (Lakoff)
Cognitive Anthropology (Berlin & Kay)
Computer Science (Zadeh)
© Stephen E. Palmer, 2002

4. The Physics of Light Light: Electromagnetic energy whose
wavelength is between 400 nm and 700 nm.
(1 nm = 10 meter) -6
© Stephen E. Palmer, 2002

5. The Physics of Light Some examples of the spectra of light sources
© Stephen E. Palmer, 2002

6. The Physics of Light
Some examples of the reflectance spectra of surfaces
Red
Yellow
Blue
Purple
% Photons Reflected
Wavelength (nm)
© Stephen E. Palmer, 2002

7. The Psychophysical Correspondence
There is no simple functional description for the perceived
color of all lights under all viewing conditions, but …...
A helpful constraint:
Consider only physical spectra with normal distributions
mean
area
variance
© Stephen E. Palmer, 2002

8. The Psychophysical Correspondence
Mean
Hue
# Photons
Wavelength
© Stephen E. Palmer, 2002

9. The Psychophysical Correspondence
Variance
Saturation
Wavelength
# Photons
© Stephen E. Palmer, 2002

10. The Psychophysical Correspondence
Area
Brightness
# Photons
Wavelength
© Stephen E. Palmer, 2002

11. Physiology of Color Vision
Two types of light-sensitive receptors
Cones
cone-shaped
less sensitive
operate in high light
color vision
Rods
rod-shaped
highly sensitive
operate at night
gray-scale vision
© Stephen E. Palmer, 2002

12. The Microscopic View

13. Rods and Cones in the Retina

14. What Rods and Cones Detect
Notice how they aren’t distributed evenly, and the rod is more sensitive to shorter wavelengths

15. Center / Surround Strong activation in center, inhibition on surround
The effect you get using these center / surround cells is enhanced edges
top: the stimuli itself
middle: brightness of the stimuli
bottom: response of the retina
You’ll see this idea get used in Regier’s model

16. How They Fire No stimuli: Stimuli in center: Stimuli in surround:
both fire at base rate
Stimuli in center:
ON-center-OFF-surround fires rapidly
OFF-center-ON-surround doesn’t fire
Stimuli in surround:
OFF-center-ON-surround fires rapidly
ON-center-OFF-surround doesn’t fire
Stimuli in both regions:
both fire slowly

17. Theories of Color Vision
Two main algorithmic theories of color vision:
Trichromatic Theory
(Palmer/Young/Helmholtz)
Hermann von Helmholtz
Opponent Process
Theory (Hering)
Ewald Hering
© Stephen E. Palmer, 2002

18. Physiology of Color Vision
Three kinds of cones: Absorption spectra
Opponent Processes:
R/G = L-M
G/R = M-L
B/Y = S-(M+L)
Y/B = (M+L)-S
Implementation of Trichromatic theory
© Stephen E. Palmer, 2002

19. Physiology of Color Vision
Opponent-Process Cells in LGN (De Valois)
Implementation of opponent process theory
(Similar color behavior in retinal ganglion cells)
© Stephen E. Palmer, 2002

20. Physiology of Color Vision
Double Opponent Cells in V1
G+R-
R+G-
Red/Green
Y+B-
B+Y-
Blue/Yellow
© Stephen E. Palmer, 2002

21. What numbers do you see in these displays?
Color Blindness
Not everybody perceives colors in the same way!
What numbers do you see in these displays?
© Stephen E. Palmer, 2002

22. Color Blindness There are several forms of inherited variations
of color vision.
Trichromatic (“normal”) color vision
Dichromatic color vision
2 forms of red-green color blindness
1 form of yellow-blue color blindness
Monochromatic color vision
4 forms
Various forms of “color weakness”
© Stephen E. Palmer, 2002

23. Color Blindness What does the world look like to a color blind person?
Normal
Trichromat
Protanope
Deuteranope
Tritanope
© Stephen E. Palmer, 2002

24. Theories of Color Vision
Opponent Process theory (Hering): All colors are
combinations of responses in three underlying
bipolar systems (Red/Green, Blue/Yellow, Black/White).
© Stephen E. Palmer, 2002

25. Theories of Color Vision
Dual Process Theory (Hurvich & Jameson): The color
vision system contains two stages: an initial trichromatic
stage and a later opponent-process stage.
Trichromatic
stage
Opponent-
Process stage
Dual Process Theory
© Stephen E. Palmer, 2002

26. Theories of Color Vision
A Dual Process Wiring Diagram
Trichromatic Stage
Opponent Process Stage
© Stephen E. Palmer, 2002

27. Surface-based processing
COLOR VISION: Part 4
1. Color Constancy:
Surface-based processing
2. Color Naming:
Category-based processing
© Stephen E. Palmer, 2002

28. Color Constancy Color Constancy: the ability to perceive the
invariant color of a surface despite ecological
Variations in the conditions of observation.
Another inverse problem:
Physics of light emission and surface reflection
underdetermine perception of surface color
© Stephen E. Palmer, 2002

29. Color Constancy Iw Lw Rw
© Stephen E. Palmer, 2002

30. Color Constancy
© Stephen E. Palmer, 2002

31. Color Constancy Two approaches to lightness constancy
Unconscious Inference (Helmholtz)
Luminance = Intensity * Reflectance
If you know L and I, you can solve for R!
Invariant Relations (Hering)
Luminance ratios are invariant with illumination
© Stephen E. Palmer, 2002

32. Luminance ratio is invariant over illumination:
Color Constancy
Luminance ratio is invariant over illumination:
Luminance Ratio = 9:1
Luminance Ratio = 9:1
© Stephen E. Palmer, 2002

33. Color Constancy The anchoring problem: What about absolute lightness?
How do we know what is white?
(How big is the anchor???)
© Stephen E. Palmer, 2002

34. Anchoring heuristic: The lightest region is taken as white

35. Surface-based processing
COLOR VISION: Part 4
1. Color Constancy:
Surface-based processing
2. Color Naming:
Category-based processing
© Stephen E. Palmer, 2002

36. Basic Color Terms (Berlin & Kay)
Color Naming
Basic Color Terms (Berlin & Kay)
Criteria:
1. Single words -- not “light-blue” or “blue-green”
2. Frequently used -- not “mauve” or “cyan”
3. Refer primarily to colors -- not “lime” or “gold”
4. Apply to any object -- not “roan” or “blond”
© Stephen E. Palmer, 2002

37. Color Naming BCTs in English Red Green Blue Yellow Black White Gray
Brown
Purple
Orange*
Pink
© Stephen E. Palmer, 2002

38. Color Naming Five more BCTs in a study of 98 languages Light-Blue Warm
Cool
Light-Warm
Dark-Cool
© Stephen E. Palmer, 2002

39. The WCS Color Chips Basic color terms: Single word (not blue-green)
Frequently used (not mauve)
Refers primarily to colors (not lime)
Applies to any object (not blonde)
FYI:
English has 11 basic color terms

40. Results of Kay’s Color Study
Stage I II
IIIa / IIIb IV V VI
VII
W or R or Y W
Bk or G or Bu
R or Y R
G or Bu Y Bk G Bu
Y+Bk (Brown)
R+W (Pink)
R + Bu (Purple)
R+Y (Orange)
B+W (Grey)
If you group languages into the number of basic color terms they have, as the number of color terms increases, additional terms specify focal colors

41. Color Naming Typical “developmental” sequence of BCTs
© Stephen E. Palmer, 2002

42. Focal Colors Color Naming Studied color categories in two ways
(Berlin & Kay)
Focal Colors
Studied color categories in two ways
Boundaries
Best examples
© Stephen E. Palmer, 2002

43. Prototypes Color Naming (Rosch) MEMORY :
Focal colors are remembered better than nonfocal colors.
LEARNING:
New color categories centered on focal colors are learned faster.
Categorization:
Focal colors are categorized more quickly than nonfocal colors.
© Stephen E. Palmer, 2002

44. Color Naming A fuzzy logical model of color naming (Kay & Mc Daniel)
Degree of
Membership
A fuzzy logical model of color naming (Kay & Mc Daniel)
Fuzzy set theory (Zadeh)
© Stephen E. Palmer, 2002

45. “Primary” color categories
Color Naming
“Primary” color categories
© Stephen E. Palmer, 2002

46. “Primary” color categories
Color Naming
“Primary” color categories
Red
Green
Blue
Yellow
Black
White
© Stephen E. Palmer, 2002

47. “Derived” color categories
Color Naming
“Derived” color categories
Fuzzy
logical
“ANDf”
© Stephen E. Palmer, 2002

48. “Derived” color categories
Color Naming
“Derived” color categories
Orange = Red ANDf Yellow
Purple = Red ANDf Blue
Gray = Black ANDf White
Pink = Red ANDf White
Brown = Yellow ANDf Black
(Goluboi = Blue ANDf White)
© Stephen E. Palmer, 2002

49. “Composite” color categories
Color Naming
“Composite” color categories
Fuzzy
logical
“ORf”
Warm = Red Orf Yellow
Cool = Blue Orf Green
Light-warm = White Orf Warm
Dark-cool = Black Orf Cool
© Stephen E. Palmer, 2002

50. Color Naming
© Stephen E. Palmer, 2002