Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of...
Transcript of Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of...
![Page 1: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/1.jpg)
Frédo Durand and Barb CutlerMIT- EECS
Color
Many slides courtesy of Victor Ostromoukhov and Leonard McMillan
![Page 2: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/2.jpg)
Color Vision 2
Why is the sky blue part II• What do you mean exactly by blue?
![Page 3: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/3.jpg)
Color Vision 3
Admin• Quiz on Thursday
– 1 sheet of notes allowed• Review session tonight 7:30
![Page 4: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/4.jpg)
Color Vision 4
Review of last week
![Page 5: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/5.jpg)
Color Vision 5
Monte Carlo Recap• Random rays to sample rendering equation• No meshing required, no special storage• No limitation
– On reflectance– On geometry
• Can be noisy (or slow )• Advanced
– Irradiance cache– Photon map
n1
![Page 6: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/6.jpg)
Color Vision 6
You believe you know it all• Color is about spectrum
and wavelength• We can get everything
from red, green and blue
• Well, life is more confusing than that!
![Page 7: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/7.jpg)
Color Vision 7
Puzzles about color• How comes a continuous spectrum ends up
as a 3D color space• Why is violet “close” to red• Primaries: 3 or 4? Which ones
– Red, blue, yellow, green– Cyan and magenta are not “spontaneous” primaries
• Color mixing• What is the color of Henry IV’s white horse?
![Page 8: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/8.jpg)
Color Vision 14
Plan• Color Vision• Color spaces• Producing color• Color effects
![Page 9: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/9.jpg)
Color Vision 15
Cone spectral sensitivity• Short, Medium and Long wavelength
wavelength
0.75
1.00
0.50
0.25
0.00400 500 600 700
S M L
![Page 10: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/10.jpg)
Color Vision 16
Cones do not “see” colors
wavelength
0.75
1.00
0.50
0.25
0.00400 500 600 700
M
![Page 11: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/11.jpg)
Color Vision 17
Cones do not “see” colors• Different wavelength, different intensity• Same response
wavelength
0.75
1.00
0.50
0.25
0.00400 500 600 700
M
![Page 12: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/12.jpg)
Color Vision 18
Response comparison• Different wavelength, different intensity • But different response for different cones
wavelength
0.75
1.00
0.50
0.25
0.00400 500 600 700
S M L
![Page 13: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/13.jpg)
Color Vision 19
von Helmholtz 1859: Trichromatic theory• Colors as relative responses
(ratios)Violet
Blue
Green
Yellow
Orange
Red
Short wavelength receptors
Medium wavelength receptors
Long wavelength receptors
Rec
epto
r Res
pons
es
Wavelengths (nm)
400 500 600 700
Viol
et
Blue
Gre
en
Yello
w
Ora
nge
Red
![Page 14: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/14.jpg)
Color Vision 20
Cones distribution• In the retina• LMS 40:20:1• No S (blue)
in retina center
![Page 15: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/15.jpg)
Color Vision 21
Metamers• Different spectrum• Same response
Wavelength (nm)
Wavelength (nm)
400 480 500 580 600 700
400 500 600 700
INTE
NSI
TYIN
TEN
SITY
![Page 16: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/16.jpg)
Color Vision 22
Color matching• Reproduce the color of a
test lampwith the addition of 3 primary lights
![Page 17: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/17.jpg)
Color Vision 23
Metamerism & light source• Metamers
under a given light source
• May not be metamersunder a different lamp
![Page 18: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/18.jpg)
Color Vision 24
Color blindness• Dalton • 8% male, 0.6% female• Genetic• Dichromate (2% male)
– One type of cone missing– L (protanope), M (deuteranope),
S (tritanope)• Anomalous trichromat
– Shifted sensitivity
![Page 19: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/19.jpg)
Color Vision 26
Color blindness test• Maze in subtle intensity contrast• Visible only to color blinds• Color contrast overrides intensity otherwise
![Page 20: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/20.jpg)
Color Vision 27
Plan• Color Vision
– Cone response, trichromats– Opponent theory– Higher-level
• Color spaces• Producing color• Color effects
![Page 21: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/21.jpg)
Color Vision 28
Remember von Helmholtz• Colors as relative responses
(ratios)Violet
Blue
Green
Yellow
Orange
Red
Short wavelength receptors
Medium wavelength receptors
Long wavelength receptors
Rec
epto
r Res
pons
es
Wavelengths (nm)
400 500 600 700
Viol
et
Blue
Gre
en
Yello
w
Ora
nge
Red
![Page 22: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/22.jpg)
Color Vision 29
Hering 1874: Opponent Colors
+
0
-
+
0
-
+
0
-
Red/Green
Receptors
Blue/Yellow
Receptors
Black/White
Receptors
• Hypothesis of 3 types of receptors: Red/Green, Blue/Yellow, Black/White
• Explains well several visual phenomena
• Hypothesis of 3 types of receptors: Red/Green, Blue/Yellow, Black/White
• Explains well several visual phenomena
![Page 23: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/23.jpg)
Color Vision 30
Dual Process Theory• The input is LMS• The output has a different
parameterization:– Light-dark– Blue-yellow– Red-green
S
L
M
G
Y
Wh
BkB
R
Trichromatic
Stage
Opponent-Process
Stage
![Page 24: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/24.jpg)
Color Vision 31
Color opponents wiring
• Sums for brightness• Differences for color opponents
B+Y-
W+B-
R +G-
ML
S M L
+ + ++
++
-- Y+
B-
B+W-
G+R-
ML
S M L
+
+
+ +
- -
- -
S-M-L S+M+L L-M -S+M+L -S-M-L M-L
![Page 25: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/25.jpg)
Color Vision 32
Simultaneous contrast• In color opponent
direction• Center-surround
R+G-
G+R-
B+Y-
Y+B-
Y+B-
R+G-
G+R-
B+Y-
![Page 26: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/26.jpg)
Color Vision 33
Land Retinex
![Page 27: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/27.jpg)
Color Vision 34
Simultaneous Color Contrast
![Page 28: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/28.jpg)
Color Vision 35
After-Image
![Page 29: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/29.jpg)
Color Vision 36
Opponent Colors
ImageImage AfterimageAfterimage
![Page 30: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/30.jpg)
Color Vision 37
Opponents and image compression• JPG, MPG• Color
opponents instead of RGB
• Compress color more than luminance
![Page 31: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/31.jpg)
Color Vision 38
Plan• Color Vision
– Cone response, trichromats– Opponent theory– Higher-level
• Color spaces• Producing color• Color effects
![Page 32: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/32.jpg)
Color Vision 39
Color reparameterization
• The input is LMS• The output has a different
parameterization:– Light-dark– Blue-yellow– Red-green
• A later stage may reparameterize:– Brightness or Luminance or Value– Hue– Saturation
S
L
M
G
Y
Wh
BkB
R
S
L (or B)
H
![Page 33: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/33.jpg)
Color Vision 40
Hue Saturation Value
Courtesy of Stephen Palmer, VISION SCIENCE, and the MIT Press.Used with permission.
![Page 34: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/34.jpg)
Color Vision 41
Hue Saturation Value• One interpretation
in spectrum space• Not the only one
because of metamerism
• Dominant wavelength (hue)
• Intensity• Purity (saturation)
![Page 35: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/35.jpg)
Color Vision 42
Color categories• Prototypes• Harder to classify colors
at boundaries
Hue0
Deg
ree
ofM
embe
rshi
p 1
Focal Blue
Focal Green
(Red) Blue Green Yellow Red (Blue)
Focal Yellow
Focal Red
![Page 36: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/36.jpg)
Color Vision 43
Plan• Color Vision• Color spaces• Producing color• Color effects
![Page 37: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/37.jpg)
Color Vision 44
Color spaces• Human color perception is 3 dimensional• How should we parameterize this 3D space• Various constraints/goals
– Linear parameterization– Close to color technology– Close to human perception– Standard
![Page 38: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/38.jpg)
Color Vision 45
The root of all evil• Cone responses are not orthogonal
(they overlap)• To change the M response without changing the
L one, we need negative light
wavelength
0.75
1.00
0.50
0.25
0.00400 500 600 700
S M L
Orthogonal basis (color matching function)
![Page 39: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/39.jpg)
Color Vision 46
Color Matching Problem
• Some colors cannot be produced using only positively weighted primaries
• E.g. primaries: pure wavelength– 650, 530, 460
• Some colors need negative amounts of primaries
• Analysis spectrum hasnegative lobes
![Page 40: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/40.jpg)
Color Vision 47
Color Matching Problem• Some colors cannot beproduced using only positively weighted primaries
• Solution: add light on the other side!
![Page 41: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/41.jpg)
Color Vision 48
Color Matching Problem
• Some colors cannot be produced using only positively weighted primaries
• Some tradeoff must be found between negative lobes in analysis vs. synthesis
• In 1931, the CIE (Commission Internationale de L’Eclairage) defined three new primaries
• Called X, Y , Z,
– with positive color matching functions
![Page 42: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/42.jpg)
Color Vision 49
CIE color space• Can think of X, Y ,
Z as coordinates
• Linear transform from RGB or LMS
x
R
z
y
3.24G -0.97B 0.06
-1.541.88
-0.20
-0.500.04
-1.06(( (( XYZ( (=
X 0.41Y 0.21Z 0.02
0.360.720.12
0.180.070.95(( (( R
GB( (=
![Page 43: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/43.jpg)
Color Vision 50
CIE color space• Odd-shaped cone contains visible colors
– Note that many points in XYZ do not correspond to visiblecolors!
x
R
z
y
3.24G -0.97B 0.06
-1.541.88
-0.20
-0.500.04
-1.06(( (( XYZ( (=
X 0.41Y 0.21Z 0.02
0.360.720.12
0.180.070.95(( (( R
GB( (=
![Page 44: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/44.jpg)
Color Vision 51
CIE color space• Objective, quantitative color descriptions
– Dominant wavelength:• Wavelength “seen” (corresponds to Hue)
– Excitation purity:• Saturation, expressed objectively
– Luminance:• Intensity
• Chromaticity (independent of luminance):– normalize against X + Y + Z:
![Page 45: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/45.jpg)
Color Vision 52
CIE color space• Spectrally pure colors lie along boundary
• Note that some huesdo not correspond to a pure spectrum (purple-violet)
• Standard white light (approximates sunlight) at C
C0.1
0.1
0.2
400480
490
500
510Green
520540
560
580Yellow
RedPurple
Blue
Cyan 600
7000.2
0.3
0.3
0.4
0.4
0.5
0.5
0.6
0.6
0.7 0.8x
y
0.70.80.9
C
Hunt, R. W. G. The Reproduction of Colour. John Wiley & Sons Incorporated. September 2004. ISBN: 0-470-02425-9.
Image adapted from:
![Page 46: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/46.jpg)
Color Vision 53
CIE color space• Match color at some point A
• A is mix of white C, spectral B!
• What is dominant wavelength of A?
• What is excitation purity (%) of A?
– Move along AC/BC
C0.1
0.1
0.2
400
480
490
500
510
520540
560B
A
D
ECF
G
580
600
7000.2
0.3
0.3
0.4
0.4
0.5
0.5
0.6
0.6
0.7x
y
0.7
0.8
Hunt, R. W. G. The Reproduction of Colour. John Wiley & Sons Incorporated. September2004. ISBN: 0-470-02425-9.
Image adapted from:
![Page 47: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/47.jpg)
Color Vision 54
XYZ vs. RGB• Linear transform
• XYZ is more standardized• XYZ can reproduce all colors with positive
values• XYZ is not realizable physically !!
– What happens if you go “off” the diagram– In fact, the orthogonal (synthesis) basis of XYZ
requires negative values.
![Page 48: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/48.jpg)
Color Vision 55
Perceptually Uniform Space: MacAdam• In color space CIE-XYZ, the
perceived distance between colors is not equal everywhere
• In perceptually uniform color space, Euclidean distances reflect perceived differences between colors
• MacAdam ellipses (areas of unperceivable differences) become circles
560550540530520510
490
480
470460 450
.05
x
y
.10 .15.20
.45.50.55.60.65
.25
.25
.20
.15
.10
.05
.35 .40 .45
Spectrum locus
.50 .55 .60.65 .70.30
400 nm
700 nm650
620610600
590580570
Purple line
Wyszecki, G. and W. S. Stiles. Color science: Concepts and Methods, Quantitative Data and Formulae. Wiley-Interscience, 2nd ed. July 2000. ISBN: 0471399183.
Image adapted from:
![Page 49: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/49.jpg)
Color Vision 56
CIE-LAB
Source: [Wyszecki and Stiles ’82]
Image adapted from Wyszecki, G., and W. S. Stiles,Color science: Concepts and methods, quantitative data and formulae.Wiley-Interscience; 2nd Edition. July 2000. ISBN: 0471399183
![Page 50: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/50.jpg)
Color Vision 57
Perceptually Uniform Space Munsell
Munsell Color Space
HueValueChroma
www.munsell.com
munsell.com
![Page 51: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/51.jpg)
Color Vision 58
Color response linear subspace• Project the infinite-D spectrum onto a subspace
defined by 3 basis functions• We can use 3x3 matrices to change the
colorspace– E.g. LMS to RGB– E.g. RGB to CIE XYZ
![Page 52: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/52.jpg)
Color Vision 59
Color response and RGB or LMS• Project the infinite-D spectrum onto a subspace defined
by 3 basis functions• Small problem: this basis is NOT orthogonal• What does orthogonal mean in our case?
• Second problem: the orthogonal basis is NOT physically realizable
![Page 53: Colordspace.mit.edu/bitstream/handle/1721.1/86191/6-837-fall...• Quiz on Thursday – 1 sheet of notes allowed • Review session tonight 7:30 Color Vision 4 Review of last week](https://reader035.fdocuments.us/reader035/viewer/2022071103/5fdd28c07185d2640c531165/html5/thumbnails/53.jpg)
Color Vision 60
Color response and RGB or LMS• Project the infinite-D spectrum onto a subspace defined
by 3 basis functions• Small problem: this basis is NOT orthogonal• What does orthogonal mean in our case?
• Second problem: the orthogonal basis is NOT physically realizable