Презентация на тему: C O L O R and the human response to light

C O L O R and the human response to light
Contents
Introduction
Electromagnetic Radiation - Spectrum
Spectral Power Distribution
Examples
The Interaction of Light and Matter
The Physiology of Human Vision
The Human Eye
The Human Retina
The Human Retina
Retinal Photoreceptors
Cones
3 Types of Cones
Cones Spectral Sensitivity
Metamers
History
3D Color Spaces
Contents
Linear Color Spaces
RGB Color Model
Color Matching Experiment
CIE-RGB
RGB Image
CMYK Color Model
Combining Colors
Example: red = magenta + yellow
CMY + Black
Example
C O L O R and the human response to light
C O L O R and the human response to light
C O L O R and the human response to light
C O L O R and the human response to light
From RGB to CMY
Color Spaces
The Artist Point of View
Munsell Color System
Munsell Book of Colors
Munsell Book of Colors
HSV/HSB Color Space
HSV
HLS Color Space
Color Spaces
CIE Color Standard
CIE Color Standard
CIE Color Standard - 1931
XYZ Spectral Power Distribution
RGB to XYZ
CIE Chromaticity Diagram
Color Naming
Blackbody Radiators and CIE Standard Illuminants
Chromaticity Defined in Polar Coordinates
Chromaticity Defined in Polar Coordinates
Chromaticity Defined in Polar Coordinates
Device Color Gamut
Color Spaces
Luminance v.s. Brightness
Weber ’ s Law
Munsell lines of constant Hue and Chroma
MacAdam Ellipses of JND (Just Noticeable Difference
Perceptual Color Spaces
Munsell Lines and MacAdam Ellipses plotted in CIE-L*u ’ v ’ coordinates
Distance should be measured in perceptual color spaces
Color Spaces
Opponent Color Spaces
YIQ Color Model
YUV Color Model
YUV - Example
Summary
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Первый слайд презентации: C O L O R and the human response to light

Idit Haran

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Слайд 2: Contents

2 Contents Introduction: The nature of light The physiology of human vision Color Spaces: Linear (RGB, CMYK) Artistic View (Munsell, HSV, HLS) Standard (CIE-XYZ) Perceptual (Luv, Lab) Opponent (YIQ, YUV) – used in TV

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Слайд 3: Introduction

3 Introduction

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Слайд 4: Electromagnetic Radiation - Spectrum

4 600 nm Wavelength in meters (m) Gamma X rays Infrared Radar FM TV AM Ultra- violet 10 -12 10 -8 10 -4 10 4 1 10 8 electricity AC Short- wave 400 nm 500 nm 700 nm Wavelength in nanometers (nm) Visible light Electromagnetic Radiation - Spectrum

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Слайд 5: Spectral Power Distribution

5 Wavelength ( l ) 400 500 600 700 0 0.5 1 Relative Power Spectral Power Distribution The Spectral Power Distribution (SPD) of a light is a function P(  ) which defines the power in the light at each wavelength

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Слайд 6: Examples

6 Examples

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Слайд 7: The Interaction of Light and Matter

7 The Interaction of Light and Matter Some or all of the light may be absorbed depending on the pigmentation of the object.

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Слайд 8: The Physiology of Human Vision

8 The Physiology of Human Vision

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Слайд 9: The Human Eye

9 The Human Eye

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Слайд 10: The Human Retina

10 The Human Retina rods cones light bipolar ganglion horizontal amacrine

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Слайд 11: The Human Retina

11 The Human Retina

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Слайд 12: Retinal Photoreceptors

12 Retinal Photoreceptors

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Слайд 13: Cones

13 Cones High illumination levels (Photopic vision) Less sensitive than rods. 5 million cones in each eye. Density decreases with distance from fovea.

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Слайд 14: 3 Types of Cones

14 3 Types of Cones L -cones, most sensitive to red light (610 nm) M- cones, most sensitive to green light (560 nm) S -cones, most sensitive to blue light (430 nm)

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Слайд 15: Cones Spectral Sensitivity

15 Cones Spectral Sensitivity

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Слайд 16: Metamers

16 Metamers Two lights that appear the same visually. They might have different SPDs (spectral power distributions)

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Слайд 17: History

17 History Tomas Young (1773-1829) “ A few different retinal receptors operating with different wavelength sensitivities will allow humans to perceive the number of colors that they do. “ James Clerk Maxwell (1872) “ We are capable of feeling three different color sensations. Light of different kinds excites three sensations in different proportions, and it is by the different combinations of these three primary sensations that all the varieties of visible color are produced. “ Trichromatic: “ Tri ” =three “ chroma ” =color

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Слайд 18: 3D Color Spaces

18 R G B Brightness Hue black-white red-green blue-yellow Cubic Color Spaces Polar Color Spaces Opponent Color Spaces 3D Color Spaces Three types of cones suggests color is a 3D quantity. How to define 3D color space?

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Слайд 19: Contents

19 Contents Introduction: The nature of light The physiology of human vision Color Spaces: Linear (RGB, CMYK) Artistic View (Munsell, HSV, HLS) Standard (CIE-XYZ) Perceptual (Luv, Lab) Opponent (YIQ, YUV) – used in TV

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Слайд 20: Linear Color Spaces

20 Linear Color Spaces Colors in 3D color space can be described as linear combinations of 3 basis colors, called primaries a · + b · + c · = The representation of : is then given by: (a, b, c)

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Слайд 21: RGB Color Model

21 RGB Color Model RGB = Red, Green, Blue Choose 3 primaries as the basis SPDs (Spectral Power Distribution.) 400 500 600 700 0 1 2 3 Wavelength (nm) Primary Intensity

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Слайд 22: Color Matching Experiment

22 Color Matching Experiment Three primary lights are set to match a test light + - + - + - test match = ~ 400 500 600 700 0 0.25 0.5 0.75 1 400 500 600 700 0 0.25 0.5 0.75 1 Test light Match light

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Слайд 23: CIE-RGB

23 (85, 38, 10) (21, 45, 72) (65, 54, 73) CIE-RGB Stiles & Burch (1959) Color matching Experiment. Primaries are: 444.4 525.3 645.2 Given the 3 primaries, we can describe any light with 3 values (CIE-RGB):

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Слайд 24: RGB Image

24 126 14 111 36 36 111 36 111 36 12 12 17 17 111 14 126 17 36 12 111 36 36 200 12 14 126 17 36 36 111 12 14 36 36 200 12 14 126 17 36 36 111 36 200 200 12 14 111 14 126 126 17 36 36 36 36 12 14 111 111 36 126 17 36 36 200 111 72 72 12 12 17 10 128 36 17 200 111 12 14 126 126 126 126 17 17 17 17 36 36 36 36 36 200 200 200 12 12 12 14 14 111 111 72 72 72 106 155 10 128 36 17 200 111 12 14 126 126 126 126 17 17 17 17 36 36 36 36 36 200 200 200 12 12 12 14 14 111 111 72 72 72 106 155 14 126 17 36 36 111 36 200 200 12 14 111 14 126 126 17 36 36 36 36 12 14 111 111 36 126 17 36 36 200 111 72 72 12 12 17 126 14 111 36 36 111 36 111 36 12 12 17 17 111 14 126 17 36 12 111 36 36 200 12 14 126 17 36 36 111 12 14 36 36 200 12 RGB Image

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Слайд 25: CMYK Color Model

25 CMYK Color Model CMYK = Cyan, Magenta, Yellow, blacK Magenta – removes Green B G R Black – removes all Yellow – removes Blue B G R B G R transmit Cyan – removes Red

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Слайд 26: Combining Colors

26 Combining Colors Additive (RGB) Subtractive (CMYK)

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Слайд 27: Example: red = magenta + yellow

27 yellow B G R + B G R red R = magenta B G R B G R Example: red = magenta + yellow

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Слайд 28: CMY + Black

28 C + M + Y = K (black) 100 50 70 = 50 0 20 50 + C M Y C M Y K CMY + Black Using three inks for black is expensive C+M+Y = dark brown not black Black instead of C+M+Y is crisper with more contrast

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Слайд 29: Example

29 Example

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Слайд 30

30 Example

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Слайд 31

31 Example

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Слайд 32

32 Example

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Слайд 33

33 Example

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Слайд 34: From RGB to CMY

34 From RGB to CMY

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Слайд 35: Color Spaces

35 Color Spaces Linear (RGB, CMYK) Artistic View (Munsell, HSV, HLS) Standard (CIE-XYZ) Perceptual (LUV, Lab) Opponent (YIQ, YUV) – used in TV

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Слайд 36: The Artist Point of View

36 The Artist Point of View Hue - The color we see (red, green, purple) Saturation - How far is the color from gray (pink is less saturated than red, sky blue is less saturated than royal blue) Brightness/Lightness (Luminance) - How bright is the color white

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Слайд 37: Munsell Color System

37 Munsell Color System Equal perceptual steps in Hue Saturation Value. Hue: R, YR, Y, GY, G, BG, B, PB, P, RP (each subdivided into 10) Value: 0... 10 (dark... pure white) Chroma: 0... 20 (neutral... saturated) Example: 5YR 8/4

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Слайд 38: Munsell Book of Colors

38 Munsell Book of Colors

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Слайд 39: Munsell Book of Colors

39 Munsell Book of Colors

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Слайд 40: HSV/HSB Color Space

40 HSV/HSB Color Space Brightness Scale Saturation Scale HSV = Hue Saturation Value HSB = Hue Saturation Brightness

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Слайд 41: HSV

41 HSV Value Saturation Hue

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Слайд 42: HLS Color Space

42 HLS Color Space red 0 ° green 120 ° yellow Blue 240 ° cyan magenta V black 0.0 0.5 H S HLS = Hue Lightness Saturation

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Слайд 43: Color Spaces

43 Color Spaces Linear (RGB, CMYK) Artistic View (Munsell, HSV, HLS) Standard (CIE-XYZ) Perceptual (Luv, Lab) Opponent (YIQ, YUV) – used in TV

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Слайд 44: CIE Color Standard

44 CIE Color Standard Why do we need a standard ? RGB differ from one device to another

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Слайд 45: CIE Color Standard

45 CIE Color Standard Why do we need a standard ? RGB differ from one device to another RGB cannot represent all colors RGB Color Matching Functions

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Слайд 46: CIE Color Standard - 1931

46 CIE Color Standard - 1931 CIE - Commision Internationale d ’ Eclairage 1931 - defined a standard system for color representation. XYZ tristimulus coordinate system. X Y Z

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Слайд 47: XYZ Spectral Power Distribution

47 XYZ Spectral Power Distribution Non negative over the visible wavelengths. The 3 primaries associated with x y z spectral power distribution are unrealizable (negative power in some of the wavelengths). y was chosen to equal luminance of monochromatic lights. Wavelength (nm) Tristimulus values 400 500 600 700 0.2 0.6 1 1.4 1.8 z( l ) y( l ) x( l )

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Слайд 48: RGB to XYZ

48 RGB to XYZ RGB to XYZ is a linear transformation 0.490 0.310 0.200 0.177 0.813 0.011 0.000 0.010 0.990 R G B X Y Z =

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Слайд 49: CIE Chromaticity Diagram

49 CIE Chromaticity Diagram Y X+Y+Z Y = y X X+Y+Z X = x x+y+z = 1 Z X+Y+Z Z = z 650 610 590 550 570 600 580 560 540 505 500 510 520 530 490 495 485 480 470 450 1.0 0.5 0.0 0.5 0.9 y 0.0 x

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Слайд 50: Color Naming

50 Color Naming x 650 610 590 550 570 600 580 560 540 505 500 510 520 530 490 495 485 480 470 450 1.0 0.5 0.0 0.5 0.9 green yellow- green yellow orange red magenta purple blue cyan white pink y

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Слайд 51: Blackbody Radiators and CIE Standard Illuminants

51 Blackbody Radiators and CIE Standard Illuminants CIE Standard Illuminants: 2500 - tungsten light (A) 4800 - Sunset 10K - blue sky 6500 - Average daylight (D65)

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Слайд 52: Chromaticity Defined in Polar Coordinates

52 Chromaticity Defined in Polar Coordinates Given a reference white. Dominant Wavelength – wavelength of the spectral color which added to the reference white, produces the given color. 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 reference white

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Слайд 53: Chromaticity Defined in Polar Coordinates

53 Chromaticity Defined in Polar Coordinates Given a reference white. 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 reference white Dominant Wavelength Complementary Wavelength - wavelength of the spectral color which added to the given color, produces the reference white.

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Слайд 54: Chromaticity Defined in Polar Coordinates

54 Chromaticity Defined in Polar Coordinates Given a reference white. 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 reference white Dominant Wavelength Complementary Wavelength Excitation Purity – the ratio of the lengths between the given color and reference white and between the dominant wavelength light and reference white. Ranges between 0.. 1. purity

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Слайд 55: Device Color Gamut

55 Device Color Gamut We can use the CIE chromaticity diagram to compare the gamut of various devices: Note, for example, that a color printer cannot reproduce all shades available on a color monitor

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Слайд 56: Color Spaces

56 Color Spaces Linear (RGB, CMYK) Artistic View (Munsell, HSV, HLS) Standard (CIE-XYZ) Perceptual (Luv, Lab) Opponent (YIQ, YUV) – used in TV

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Слайд 57: Luminance v.s. Brightness

57 Luminance v.s. Brightness Luminance Brightness (intensity) vs (Lightness) Y in XYZ V in HSV Luminance D I1 D I2 I2 I1 I1 < I2, D I1 = D I2 Equal intensity steps: Equal brightness steps:

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Слайд 58: Weber ’ s Law

58 Weber ’ s Law In general, D I needed for just noticeable difference (JND) over background I was found to satisfy: D I I = constant ( I is intensity, D I is change in intensity) Weber’s Law: Perceived Brightness = log ( I ) Intensity Perceived Brightness

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Слайд 59: Munsell lines of constant Hue and Chroma

59 Munsell lines of constant Hue and Chroma x y 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.1 0.2 0.3 0.4 0.5 Value =1/

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Слайд 60: MacAdam Ellipses of JND (Just Noticeable Difference

60 MacAdam Ellipses of JND (Just Noticeable Difference 0.2 0.4 0.6 0.8 0 y 0.2 0.4 0.6 0 x (Ellipses scaled by 10)

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Слайд 61: Perceptual Color Spaces

61 Perceptual Color Spaces An improvement over CIE-XYZ that represents better uniform color spaces The transformation from XYZ space to perceptual space is Non Linear. Two standard adopted by CIE are L*u ’ v ’ and L*a*b* The L* line in both spaces is a replacement of the Y lightness scale in the XYZ model, but it is more indicative of the actual visual differences.

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Слайд 62: Munsell Lines and MacAdam Ellipses plotted in CIE-L*u ’ v ’ coordinates

62 Munsell Lines and MacAdam Ellipses plotted in CIE-L*u ’ v ’ coordinates u * -150 -100 -50 0 50 100 150 -150 Value =5/ 200 100 50 0 -50 -100 v * u * -150 -100 -50 0 50 100 150 200 -150 100 50 0 -50 -100 v *

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Слайд 63: Distance should be measured in perceptual color spaces

63 Distance should be measured in perceptual color spaces

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Слайд 64: Color Spaces

64 Color Spaces Linear (RGB, CMYK) Artistic View (Munsell, HSV, HLS) Standard (CIE-XYZ) Perceptual (Luv, Lab) Opponent (YIQ, YUV) – used in TV

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Слайд 65: Opponent Color Spaces

65 Opponent Color Spaces + black-white red-green blue-yellow + + - - -

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Слайд 66: YIQ Color Model

66 YIQ Color Model YIQ is the color model used for color TV in America (NTSC= National Television Systems Committee) Y is luminance, I & Q are color (I=red/green,Q=blue/yellow) Note: Y is the same as CIE ’ s Y Result: backwards compatibility with B/W TV! Convert from RGB to YIQ: The YIQ model exploits properties of our visual system, which allows to assign different bandwidth for each of the primaries (4 MHz to Y, 1.5 to I and 0.6 to Q)

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Слайд 67: YUV Color Model

67 YUV Color Model YUV is the color model used for color TV in Israel (PAL), and in video. Also called YCbCr. Y is luminance as in YIQ. U and V are blue and red (Cb and Cr). The YUV uses the same benefits as YIQ, (5.5 MHz for Y, 1.3 for U and V). Converting from RGB to YUV: Y = 0.299R + 0.587G + 0.114B U = 0.492(B – Y) V = 0.877(R – Y)

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Слайд 68: YUV - Example

68 YUV - Example U V Y

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Последний слайд презентации: C O L O R and the human response to light: Summary

69 Summary Light  Eye (Cones,Rods)  [l,m,s]  Color Many 3D color models: Reproducing Metamers to Colors Different reproduction Gamut More / Less intuitive CIE standards

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