2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2002 1
Psychophysics of colour
perception
Neurophysiology, psych...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 202
Why have colour vision?
• Why don’t other mammals have colou...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 203
The neurophysiology of colour
vision
• Rods and cones
– Rods...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 204
Cone wavelength ranges
S M L
Wavelength (nm)
Relativeabsorpt...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 205
Cone Distributions
• Where is the
fovea?
• Why is blue a
“ba...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 206
Young-Helmholtz theory of colour
• 3 primaries needed to pro...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 207
Weaknesses of the YH colour
theory• red-green are mutually e...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 208
Weaknesses of the YH colour
theory• blue-yellow are mutually...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 209
Patching up the YH colour theory
• Hering theorized opponent...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2010
Modern opponent process theory
• different combinations of ...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2011
Colour opponent channels
• achromatic:
– M+L cone
• blue-ye...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2012
What is colour?
• Property of objects?
• Property of light?...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2013
Physical dimension
e.g. wavelength
Psychologicaldimension
e...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2014
Colour experiments
• determine number of distinguishable co...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2015
Colour similarity
• resulting ordering seems to be cyclic
•...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2016
Colour similarity
• white and black correspond to saturatio...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2017
HSV: Hue, Saturation and Value
• Hue: spectral hues + mixed...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2018
high
low
high
low
HSV: Hue, Saturation and Value
Hue Satura...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2019
hue
HSV: a psychological colour space
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2020
saturation
HSV: a psychological colour space
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2021
low
high
brightness
medium
HSV: a psychological colour space
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2022
white
black
HSV: a psychological colour space
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2028
Colour constancy
• Discounting the spectral distribution of...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2029
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2030
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2031
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2032
Congenital colour deficiency
• Approximately 8% of the popu...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2033
Colour vision tests
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2034
Colour vision tests
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2035
Normal colour vision
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2036
Protanopia
L-cone, red/green deficient
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2037
Deuteranopia
M-cone, red/green deficient
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2038
Tritanopia:
S-cone, blue/yellow deficient
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2039
Normal Tritanopia
DeuteranopiaProtanopia
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2040
• Bilateral damage to V4 results in
achromatopsia
• “she lo...
2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2041
Benham, Fechner disks
• Black and white patterns that produ...
Upcoming SlideShare
Loading in...5
×

2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2002

318
-1

Published on

Published in: Technology, Business
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
318
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
4
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2002

  1. 1. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2002 1 Psychophysics of colour perception Neurophysiology, psychophysics, and magic (or you only though you knew what colour was…)
  2. 2. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 202 Why have colour vision? • Why don’t other mammals have colour vision? • Why do bees have colour vision? • Is hue or luminance more useful? • Is hue or luminance more accurate?
  3. 3. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 203 The neurophysiology of colour vision • Rods and cones – Rods are inhibited during day light – Cones are “blind” during night light • Three different types of cones, each optimally responsive to a different wavelength 1. L-Cone: long wavelength, red 2. M-Cone: medium wavelength, green 3. S-Cone: short wavelength, blue • Each type responds to a range of wavelengths
  4. 4. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 204 Cone wavelength ranges S M L Wavelength (nm) Relativeabsorption 400 500 600 700
  5. 5. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 205 Cone Distributions • Where is the fovea? • Why is blue a “bad” colour?
  6. 6. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 206 Young-Helmholtz theory of colour • 3 primaries needed to produce any spectral colour • 3 cones found in the retina • simplest colour vision theory: – cones transduce light and send signals directly to brain
  7. 7. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 207 Weaknesses of the YH colour theory• red-green are mutually exclusive (opponency): – a red light can have a blue or yellow tint but not a green tint – a green light can have a blue or yellow tint but not a red tint purple orange brown cyan yellow-green brown
  8. 8. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 208 Weaknesses of the YH colour theory• blue-yellow are mutually exclusive (opponency): – a blue light can have a red or green tint but not a yellow tint – a yellow light can have a red or green tint but not a blue tint purple orangegrey cyan yellow-green grey
  9. 9. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 209 Patching up the YH colour theory • Hering theorized opponent channels – one type of colour receptor – three colour channels: • Red/Green, Yellow/Blue, White/Black – also explains coloured afterimages – does not explain colour matching • (requires 3 types of colour receptor) • Modern opponent process theory: – combine Young-Helmholtz and Hering
  10. 10. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2010 Modern opponent process theory • different combinations of three cone types are fed into the channels: – achromatic: M+L cone responses – blue-yellow: M+L versus S cone responses – red-green: L+S versus M cone responses • chromatic channels are weighted so that they give a zero response to white
  11. 11. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2011 Colour opponent channels • achromatic: – M+L cone • blue-yellow: – M+L versus S cone • red-green: – L+S versus M cone S M L 400 500 600 700 Relativeefficiency
  12. 12. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2012 What is colour? • Property of objects? • Property of light? • Property of our brain?
  13. 13. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2013 Physical dimension e.g. wavelength Psychologicaldimension e.g.colour ? Psychophysics of colour
  14. 14. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2014 Colour experiments • determine number of distinguishable colours – JNDs • determine number of “necessary colours” • organize the colours according to similarity
  15. 15. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2015 Colour similarity • resulting ordering seems to be cyclic • where should white and black go? • where is purple?
  16. 16. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2016 Colour similarity • white and black correspond to saturation and brightness
  17. 17. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2017 HSV: Hue, Saturation and Value • Hue: spectral hues + mixed colours like purple • Saturation: purity of colour • Value: brightness or intensity purple!
  18. 18. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2018 high low high low HSV: Hue, Saturation and Value Hue Saturation Value
  19. 19. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2019 hue HSV: a psychological colour space
  20. 20. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2020 saturation HSV: a psychological colour space
  21. 21. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2021 low high brightness medium HSV: a psychological colour space
  22. 22. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2022 white black HSV: a psychological colour space
  23. 23. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2028 Colour constancy • Discounting the spectral distribution of the light source – Incandescent lights are reddish – Sun is yellowish – Sun setting is orange • Similar to lightness constancy
  24. 24. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2029
  25. 25. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2030
  26. 26. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2031
  27. 27. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2032 Congenital colour deficiency • Approximately 8% of the population (1 in 12) • Sex linked genes on X-chromosome – mostly men (women possibly tetrachromats) • Three types: missing or abnormal 1. protanopia/protoanomaly: L-cones 2. deuteranopia/deuteranomaly: M-cones 3. tritanopia: missing S-cones S M L
  28. 28. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2033 Colour vision tests
  29. 29. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2034 Colour vision tests
  30. 30. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2035 Normal colour vision
  31. 31. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2036 Protanopia L-cone, red/green deficient
  32. 32. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2037 Deuteranopia M-cone, red/green deficient
  33. 33. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2038 Tritanopia: S-cone, blue/yellow deficient
  34. 34. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2039 Normal Tritanopia DeuteranopiaProtanopia
  35. 35. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2040 • Bilateral damage to V4 results in achromatopsia • “she looked like a rat”, Rama p. 73 • Neurons in V4 respond to colours (not wavelengths) Cerebral Achromatopsia
  36. 36. 2002/02/05 PSYC202-005, Term 2, Copyright Jason Harrison, 2041 Benham, Fechner disks • Black and white patterns that produce colours – flickering monochromatic light below 40Hz • Colour is sensation NOT just physics • Does colour exist “out there”? Or “up here”?
  1. A particular slide catching your eye?

    Clipping is a handy way to collect important slides you want to go back to later.

×