colour perception

2.1 Color Perception PSYC 579 Topic Presentation, University of British Columbia

Diliara Nasirova

School of Interactive Art and Technology, Simon Fraser University

January 26, 2011

2

Outline

1.  The Physical Description of Light ■  Light Components ■  Electromagnetic Spectrum

2.  The Psychological Description of Color ■  Color Space

3.  Theories of Color Vision ■  Trichromatic Theory ■  Opponent Process Theory

Diliara Nasirova | PSYC 579 | Jan 26, 2011

4.  Basic Phenomena ■  Color Blindness ■  Color Afterimage ■  Color Contrast

5.  Application to Visual Design ■  Color Specification Interfaces ■  Color for Labeling

3

References

1.  C. Ware, “Information Visualization: Perception for Design”, ch. 4 “Color” 2.  SE. Palmer, “Vision Science”

3.  E. Tufte, “Envisioning Information”, ch. 5 “Color and information” 4.  P Rheingans. (1999). “Task-based Color Scale Design” 5.  CA Brewer. (2005). “Designing Better Maps”, ch. 5 “Color Decisions for

Mapping”

6.  C. Ware, “Visual Thinking for Design”, ch. 4 “Color” 7.  M. Stone, “Color in Information Display” workshop, Vis08

Diliara Nasirova | PSYC 579 | Jan 26, 2011

4

The Physical Description of Light Light Components

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  Sir Isaac Newton, 1666

5

The Physical Description of Light Electromagnetic Spectrum

Diliara Nasirova | PSYC 579 | Jan 26, 2011

6

The Psychological Description of Color Color Space

•  All colors experiences can be described in terms of three dimensions: ■  Hue ■  Value (lightness) ■  Saturation (chroma)

Diliara Nasirova | PSYC 579 | Jan 26, 2011

7

The Psychological Description of Color Color Space

•  Color space: ■  A three dimensional coordinate

system ■  Each color can be represented as a

single point with a unique position.

Diliara Nasirova | PSYC 579 | Jan 26, 2011

8

The Psychological Description of Color Color Space

•  Color solid: Subset of color space

Diliara Nasirova | PSYC 579 | Jan 26, 2011

Lightness

Hue

Saturation

9

Theories of Color Vision Trichromatic Theory

•  Trichromacy: Three color receptors (cones) in retinas that are active at normal light levels

•  Young-Helmholtz Trichromatic Theory

Diliara Nasirova | PSYC 579 | Jan 26, 2011

10

The Physical Description of Light Spectral Diagram

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  Human cone sensitivity functions.

•  Cones sensitive to ■  S (blue) ■  M (green) ■  L (red)

11

The Physical Description of Light Spectral Diagram: Short wavelength sensitive cones

Diliara Nasirova | PSYC 579 | Jan 26, 2011

Blue text on a dark background is to be avoided. We have very few short-wavelength sensitive cones in the retina and they are not very sensitive.

Blue text on a dark background is to be avoided. We have very few short-wavelength sensitive cones in the retina and they are not very sensitive.

12

The Physical Description of Light Spectral Diagram: Short wavelength sensitive cones

Diliara Nasirova | PSYC 579 | Jan 26, 2011

Blue text on a dark background is to be avoided. We have very few short-wavelength sensitive cones in the retina and they are not very sensitive.

Blue text on a dark background is to be avoided. We have very few short-wavelength sensitive cones in the retina and they are not very sensitive.

13

Theories of Color Vision Opponent Process Theory

•  Ewald Hering Opponent Process Theory

•  Six elementary colors arranged as opponent pairs along three axes: ■  black-white, ■  red-green, ■  yellow-blue.

Diliara Nasirova | PSYC 579 | Jan 26, 2011

14

Theories of Color Vision Opponent Process Theory: Physiological basis

•  Input from the cones is processed into 3 distinct channels

Diliara Nasirova | PSYC 579 | Jan 26, 2011

15

Theories of Color Vision Opponent Process Theory: Scientific evidence

1.  Unique Hues: black, white, red, green…

Diliara Nasirova | PSYC 579 | Jan 26, 2011

16

Theories of Color Vision Opponent Process Theory: Scientific evidence

2.  Naming and Cross-Cultural Naming:

“yellowish green”, but no “yellowish blue”

Diliara Nasirova | PSYC 579 | Jan 26, 2011

17

3.  Neurophysiology: cells in visual cortexes of monkeys that have properties of opponency

Diliara Nasirova | PSYC 579 | Jan 26, 2011

Theories of Color Vision Opponent Process Theory: Scientific evidence

18

3.  Categorical Colors:

■  Evidence that confusion between colors is affected by color categories

Diliara Nasirova | PSYC 579 | Jan 26, 2011

Theories of Color Vision Opponent Process Theory: Scientific evidence

19 Diliara Nasirova | PSYC 579 | Jan 26, 2011

Theories of Color Vision Opponent Process Theory: Scientific evidence

20

Theories of Color Vision Opponent Process Theory: Color Channels Properties

•  Chromatic channels carry ~1/3 the amount of detail carried by the black–white channel.

•  Difficult to read the text where luminance is equal, despite a large chromatic difference

Diliara Nasirova | PSYC 579 | Jan 26, 2011

21

Theories of Color Vision Opponent Process Theory: Color Channels Properties

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  Form: Form perception processed mainly through the luminance channel

Floor, Duomo di Siena

22

Theories of Color Vision Opponent Process Theory: Color Channels Properties

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  Form: Pseudocolor sequences for maps

23

Basic Phenomena Color Contrast

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  Colors are perceived relative to their overall context

24

Basic Phenomena Color Blindness

•  ~10% of the male and ~1% of the female population have some form of color vision deficiency.

Original

Deuteranope (r/g)

Protanope (r/g)

Tritanope (y/b)

25

Basic Phenomena Color Blindness

Diliara Nasirova | PSYC 579 | Jan 26, 2011

26

Basic Phenomena Color Blindness

Diliara Nasirova | PSYC 579 | Jan 26, 2011

Normal vision: no number Color blind vision: “45”

27

Basic Phenomena Color Afterimage

Diliara Nasirova | PSYC 579 | Jan 26, 2011

28

Basic Phenomena Color Afterimage

Diliara Nasirova | PSYC 579 | Jan 26, 2011

.

29

Basic Phenomena Color Afterimage

•  BMW commercial: http://www.huffingtonpost.com/2010/12/16/bmw-ad-vide-burns-logo-into-eyes-_n_797981.html

Diliara Nasirova | PSYC 579 | Jan 26, 2011

30

Application to Visual Design Color Specification Interfaces

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  One of the most widely used color interfaces in computer graphics is based on the HSV color space

saturation

hue value

31

Application to Visual Design Color Specification Interfaces

Diliara Nasirova | PSYC 579 | Jan 26, 2011

32

Application to Visual Design Color for Labeling

•  Labeling: nominal information coding

•  Color can be extremely effective as a nominal code.

Diliara Nasirova | PSYC 579 | Jan 26, 2011

33

Application to Visual Design Color for Labeling

•  Perceptual factors to be considered: 1.  Distinctness 2.  Unique hues 3.  Contrast with background 4.  Color blindness 5.  Number 6.  Field size 7.  Conventions

Diliara Nasirova | PSYC 579 | Jan 26, 2011

34

Application to Visual Design Color for Labeling

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  Perceptual factors to be considered: 1.  Distinctness 2.  Unique hues 3.  Contrast with background 4.  Color blindness 5.  Number 6.  Field size 7.  Conventions

35

Application to Visual Design Color for Labeling

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  Perceptual factors to be considered: 1.  Distinctness 2.  Unique hues 3.  Contrast with background 4.  Color blindness 5.  Number 6.  Field size 7.  Conventions

36

Application to Visual Design Color for Labeling

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  Perceptual factors to be considered: 1.  Distinctness 2.  Unique hues 3.  Contrast with background 4.  Color blindness 5.  Number 6.  Field size 7.  Conventions

37

Application to Visual Design Color for Labeling

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  Perceptual factors to be considered: 1.  Distinctness 2.  Unique hues 3.  Contrast with background 4.  Color blindness 5.  Number 6.  Field size 7.  Conventions

38

Application to Visual Design Color for Labeling

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  Perceptual factors to be considered: 1.  Distinctness 2.  Unique hues 3.  Contrast with background 4.  Color blindness 5.  Number 6.  Field size 7.  Conventions

39

Application to Visual Design Color for Labeling

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  Perceptual factors to be considered: 1.  Distinctness 2.  Unique hues 3.  Contrast with background 4.  Color blindness 5.  Number 6.  Field size 7.  Conventions

40

Application to Visual Design Color for Labeling

Diliara Nasirova | PSYC 579 | Jan 26, 2011

•  12 colors recommended for use in coding.

41

Conclusion