SLIDE 1 H517 Visualization Design, Analysis, & Evaluation
Khairi Reda | redak@iu.edu School of Informa5cs & Compu5ng, IUPUI
Week 4: Color Perception
SLIDE 2 Paper presentations
- Every week we will have 2 papers, each paper will be
presented by two students
- Prepare a PowerPoint presenta5on about the paper (15
minutes)
- Cri5que the authors’ work: What are the main claims? Did
the authors present enough evidence to back them up? Do you like the paper? What would you change about it?
- Lead a discussion (15 minute)
- End your presenta5on with ini5al ques5ons for the class
- Everyone should read the paper before coming to class
- Asking ques5ons and providing comments will count
towards your 10% par5cipa5on grade
SLIDE 3
Last week…
SLIDE 4 Visual perception
http://www.fortworthastro.com/images/eye_xsection_01.jpg
light electricity
SLIDE 5
Visual Thinking for Design
SLIDE 6
POPOUT
SLIDE 7
POPOUT
SLIDE 8 Take home point
Our visual system sees differences, not absolute values
Based on a slide by Miriah Meyer
SLIDE 9
Visual perception is relative
Differences in contrast is rela5ve
SLIDE 10
Visual perception is relative
Sizes are rela5ve (Ames room)
SLIDE 11 color
The Huffington Post
SLIDE 12 color
the property possessed by an object of producing different sensa5ons on the eye as a result of the way the
- bject reflects or emits light
- Oxford dictionary
SLIDE 13 Electromagne5c radia5on within a certain range [400nm
- 700nm] of the electromagne5c spectrum
more energy
light
SLIDE 14 Mariah Meyer
light
SLIDE 15
Trichromacy
SLIDE 16 Trichromacy
Normal human color vision is 3 dimensional Derived from three cone types (short, medium, and long wave-length sensi5vity) Each type of cone contains a specific photosensi5ve pigment that reacts to a certain wavelength of light
Based on a slide by Mariah Meyer
SLIDE 17
Trichromacy
difficult to read easy to read difficult to read easy to read
SLIDE 18 Explains how signals are processed
Opponent-process theory
Visual perceptual system detects differences in the response of cones
+
luminance
- red-green
- pponent channel
+
yellow-blue
SLIDE 19
SLIDE 20 Explains how signals are processed
Opponent-process theory
Visual perceptual system detects differences in the response of cones
+
luminance
- red-green
- pponent channel
+
yellow-blue
SLIDE 21
“Important” colors
These colors have a name in virtually every human language Their seman5cs and connota5ons are culture- specific
SLIDE 22
- C. Ware, Visual Thinking for Design
Sensitivity to spatial detail
The luminance channel has greater ability to resolve smaller detail
SLIDE 23
- C. Ware, Visual Thinking for Design
Sensitivity to spatial detail
SLIDE 24
Color deficiencies
SLIDE 25 Color deficiencies
Some5mes caused by faculty cones, some5mes by faulty pathways red-green weakness is the most common type 8% of (North American) makes, 0.5% of female
Based on a slide by Miriah Meyer
normal re5na Protanopic
SLIDE 26 Via Miriah Meyer
lacking green cones lacking red cones lacking blue cones
SLIDE 27
SLIDE 28 difficult to dis5nguish for people with Deuteranopia
SLIDE 29 Color spaces
Representing color with numbers
SLIDE 30 light
- 1. pure yellow: 580 nm
- 2. color matching
yellow
SLIDE 31
red green blue
Tristimulus color matching
test color
SLIDE 32
red green blue
Tristimulus color matching
test color 580nm
SLIDE 33 Tristimulus color matching
red green blue
0.17 0.17
test color 580nm
SLIDE 34
Tristimulus color matching
red green blue test color 580nm
SLIDE 35
Tristimulus color matching
red green blue test color 580nm
SLIDE 36
SLIDE 37
SLIDE 38
SLIDE 39 RGB color space
Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color
1.0 1.0 1.0
Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color G B R
SLIDE 40 1.0 1.0 1.0
yellow (1.0, 1.0, 0.0)
RGB color space
Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color
SLIDE 41 RGB color space
1.0 1.0 1.0
Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color
(1.0, 0.6, 0.4)
SLIDE 42 1.0 1.0 1.0
white (1.0, 1.0, 1.0)
RGB color space
1.0 1.0 1.0
Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color
SLIDE 43 1.0 1.0 1.0
black (0.0, 0.0, 0.0)
RGB color space
1.0 1.0 1.0
Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color
SLIDE 44 what colors combinaCon can be used to re- producing the visible light spectrum by mixing?
- red, yellow, blue
- red, green, blue
- range, green, violet
- cyan, magenta, yellow
- all of the above
Miriah Meyer
SLIDE 45
Light mixing (RGB)
Addi5ve mixing of colored lights
SLIDE 46 Light mixing (RGB)
LCD display closeup
Wikipedia
SLIDE 47
Ink mixing (CMY / CMYK)
Subtrac5ve mixing of inks printed on white paper
SLIDE 48 Color picture CMY composite
Wikipedia
CMYK composite
SLIDE 49
- red, yellow, blue
- red, green, blue
- range, green, violet
- cyan, magenta, yellow
- all of the above
Miriah Meyer
, almost
what colors combinaCon can be used to re- producing the visible light spectrum by mixing?
SLIDE 50
SLIDE 51
red green blue test color 500nm
Tristimulus color matching
SLIDE 52
green blue test color 500nm
Tristimulus color matching
red
SLIDE 53
red green blue test color 500nm
Tristimulus color matching
SLIDE 54
green blue test color 500nm red
Tristimulus color matching
SLIDE 55
Opps
SLIDE 56 CIE color space
- At a mee5ng in of the CIE in 1931
- Let’s have imaginary primary colors!
- Construct linear, possibly non-realizable combina5ons of
primaries so that color matching func5ons are posi5ve throughout the visible light
- X, Y, Z primaries
- Can be linearly transformed from RGB (and vice versa)
Based on a slide by Siddhartha Chaudhuri
SLIDE 57
CIE color space
SLIDE 58 Y Z X
1.0 1.0 1.0
Y Z X
SLIDE 60
CIE chromaticity diagram
SLIDE 61 CIE chromaticity diagram
White
SLIDE 62 CIE chromaticity diagram
White
SLIDE 63 CIE chromaticity diagram
R G Y
SLIDE 64 CIE chromaticity diagram
RGB color space
SLIDE 65 Perceptual color spaces
A change in the amount of color value should produce a propor5onal change in the way we see the color
Via Miriah Meyer
SLIDE 66 HSL
- hue: what people think of as
color
- saturation: the vividness of
the color
- luminance: amount of black
mixed in
SLIDE 67
hue saturation luminance
SLIDE 68
Guidelines for using color in visualization
SLIDE 69 Colormap
Specifies a mapping between color and values
[0, 8]
SLIDE 70 Order these colors…
Miriah Meyer
SLIDE 71 Order these colors…
Miriah Meyer
SLIDE 72 Order these colors…
Miriah Meyer
SLIDE 73 colormaps for ordered data should vary monotonically in luminance Hue alone is good for categorical data Categorical colors are easier to remember if they are nameable
guidelines
Colin Ware
SLIDE 74 the rainbow colormap
temperature
SLIDE 75 the rainbow colormap
SLIDE 76
the rainbow colormap
sharp boundary
SLIDE 77
the rainbow colormap
not color blind safe
SLIDE 78
the rainbow colormap
Rainbow colormaps should be avoided as a default op5on for ordered data A safer, more effec5ve op5on is a colormap that varies in luminance. Ideally luminance and hue.
SLIDE 80 Simultaneous contrast
Via Colin Ware
SLIDE 81 Color Brewer Color Oracle
http://colororacle.org colorbrewer2.org/
Color design tools
Colorgorical
http://vrl.cs.brown.edu/color
SLIDE 82
Next week
Marks and channels: the visualiza5on alphabet (chapter 5)
SLIDE 83 D3 lab
hUps://Cnyurl.com/y9z8gefr
hUp://vis.ninja/teaching/2018/H517/d3-excercises/
