Vision and Color Perception Lecture 5 January 28, 2020 Slides - - PowerPoint PPT Presentation

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Vision and Color Perception Lecture 5 January 28, 2020 Slides - - PowerPoint PPT Presentation

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CS530 - Spring 2020 Introduction to Scientific Visualization Vision and Color Perception Lecture 5 January 28, 2020 Slides acknowledgment: P. Rheingans (UMBC) and A. Lex (Utah) Outline Preamble: human vision Physiological basis of

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January 28, 2020

CS530 - Spring 2020

Introduction to Scientific Visualization

Vision and Color Perception

Lecture 5

Slides acknowledgment: P. Rheingans (UMBC) and A. Lex (Utah)

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Outline

  • Preamble: human vision
  • Physiological basis of color

perception

  • Color vision models
  • Color spaces

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Functions of Human Vision

  • Shape/size
  • Depth
  • Motion
  • Recognition

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Properties of Vision

  • Accurate relative to other senses
  • Location, size, and identification at a distance
  • But…

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020 5

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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7 CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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Perceived Sizes Are Relative

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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Perceived Sizes Are Relative

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10 CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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Ames Room

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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Ponzo Illusion

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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Ponzo Illusion

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

  • Limitations
  • Veridical perception is limited
  • Absolute judgments are often poor
  • Lack of quantification

Properties of Vision

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Properties of Vision

  • Good at
  • Relative judgments
  • Time and space
  • Identification

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Light

  • Visible range: 390-700nm
  • Luminance has a large dynamic range
  • Colors result from spectral curves
  • dominant wavelength, hue
  • brightness, lightness
  • purity, saturation

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Light

  • Visible range: 390-700nm
  • Luminance has a large dynamic range
  • Colors result from spectral curves
  • dominant wavelength, hue
  • brightness, lightness
  • purity, saturation

18

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Light

  • Visible range: 390-700nm
  • Luminance has a large dynamic range
  • Colors result from spectral curves
  • dominant wavelength, hue
  • brightness, lightness
  • purity, saturation

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  • 0.00003 -- Moonless overcast night sky
  • 30 -- Sky on overcast day
  • 3000 -- Sky on clear day
  • 16,000 -- Snowy ground in full sunlight
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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Light

  • Visible range: 390-700nm
  • Luminance has a large dynamic range
  • Colors result from spectral curves
  • dominant wavelength, hue
  • brightness, lightness
  • purity, saturation

18

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Spectral Curve (of incoming radiation)

19 Wavelength (1/frequency) Magnitude/Intensity Visible

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Physiology: Eye

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Perspective Projection and Image Formation

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Lens Scene Image plane/retina

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Physiology: Photoreceptors

  • Discrete sensors that measure energy
  • Adaptation
  • Rods ~ 120 million
  • Active at low light levels (scotopic vision)
  • Only one wavelength-sensitivity function
  • Cones ~ 6-7 million
  • Active at normal light levels (photoptic)
  • Three types: sensitivity functions with different peaks

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Retina

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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Cone Sensitivity

24 HyperPhysics, Georgia State University

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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Rod Sensitivity Function

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020 26

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Retinotopic Mapping

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Human Gaze

  • Vision made up of fixations and

saccades

  • Fixation: 200-600 ms
  • Motion: 20-100 ms

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29 CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Models of Color Vision

  • Tricolor theory
  • Opponent process theory

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Trichromatic Theory

  • Three types of cones – each with a

characteristic wavelength

  • Mixture of 3 responses defines color
  • Explains some psychophysical data
  • 3D color space (i.e. 3 colors match

any perceived)

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Trichromatic Theory

  • Metamers: match of an apparent color

with a different spectral distribution (3D basis)

  • Color blindness (different types)

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Trichromatic Theory

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Trichromatic Theory Shortcomings

  • Color blindness
  • R-G, B-Y, All
  • Yellow seems primary
  • Color constancy

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Note: Additive vs. Subtractive Colors

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Additive Subtractive

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Note: Additive vs. Subtractive Colors

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Additive coloring: Colors are produced by combining (adding) electromagnetic radiations of different wavelength / frequency. Example: computer screen

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Note: Additive vs. Subtractive Colors

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Additive

Subtractive coloring: Colors are obtained by combining things that absorb different portions

  • f the visual spectrum when they

reflect/scatter the incoming light. Subtractive coloring defines the “color” of objects. Example: pigments of paint

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Color Blindness

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No L cones

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Color Blindness

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No M cones

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Color Blindness

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No L cones No M cones

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Color Blindness

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No L cones No M cones

Red/green deficiencies

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Color Blindness

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No S cones

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Color Blindness

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No S cones

Blue/yellow deficiency

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Luminance, Lightness, Brightness

Luminance: measured amount of light (luminous intensity per area) Brightness: perceived amount of light Lightness: perceived reflectance of a

  • surface. Lightness of a color

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Opponent Color Theory

  • Humans encode colors by

differences

  • E.g R-G, and B-Y Differences
  • Color blindness

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Perceptual Distortion

  • Color-deficiency
  • Interactions between color components
  • brightness/hue (Bezold-Brucke phenomenon)
  • saturation/brightness (Helmholtz-Kohlrausch effect)
  • Simultaneous contrast
  • brightness
  • hue
  • Small field achrominance
  • Effects of color on perceived size

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Bezold-Brucke Phenomenon

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Hurvich ‘81, pg. 73. Change in HUE perception as the INTENSITY changes

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Bezold-Brucke Phenomenon

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Helmholtz-Kohlraush effect

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brightness increased by saturation

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Simultaneous Brightness Contrast

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Simultaneous Brightness Contrast

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Simultaneous Brightness Contrast

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Perceived brightness depends on background

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Simultaneous Brightness Contrast

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  • 05. Vision and Color Perception

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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Chromatic Adaptation

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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Chromatic Adaptation

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(87, 89, 87)

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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Chromatic Adaptation

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(63, 75, 104)

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Color-size Illusion

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Color Spaces

  • Perceptually based
  • Device independent, perceptually uniform

CIELUV, CIELAB, Munsell

  • Device-derived
  • Convenient for describing display device levels

RGB, CMY

  • Intuitive (transformations)
  • Based on familiar color description terms

HSV, HSB, HLS

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

The Space of Human Color

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  • CIE 1931 XYZ
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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

CIE Color Space

  • Humans can mimic any pure light by

addition (and subtraction) of 3 primaries

  • Color is a 3D space
  • With R-G-B, addition and subtraction

are both required to get all wavelengths

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

CIE Color Space

  • In nature, light adds (but does not subtract)
  • Conversion to another coordinate system

X-Y-Z is a convenience — they are not primary colors

  • Any 3 primaries (additive) can produce
  • nly a subset of all visible colors

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

The Chromaticity Diagram

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

RGB Color Space

  • Convenient colors (screen pixel LEDs)
  • Decent coverage of the human color
  • Not a particularly good basis for human

interaction

  • Non-intuitive
  • Non-orthogonal (perceptually)

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

RGB Cube

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

The Chromaticity Diagram

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  • 05. Vision and Color Perception

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HSV

Hue: Saturation: Value:

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  • 05. Vision and Color Perception

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HSL

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L: lightness: from dark (black) to light (white)

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

RGB to HSV

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V = M = max(R, G, B); m = min(R, G, B); S = (M – m)/M; if (R==M) h = (G-B)/(M-m); if (G==M) h = 2 + (B-R)/(M-m); if (B==M) h = 4 + (R-G)/(M-m); if (h<0) H = h/6 + 1; if (h>0) H = h/6;

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Visual Popout

  • Also known as “preattentive

processing”

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Difference in hue

Images by C.H. Healy, NCSU

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Visual Popout

  • Also known as “preattentive

processing”

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Difference in curvature

Images by C.H. Healy, NCSU

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

01/28/2020

Change Blindness

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CS530 / Spring 2020 : Introduction to Scientific Visualization.

  • 05. Vision and Color Perception

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Change Blindness