Visual Imaging and the Electronic Age Color Science

Transcription

1 Visual Imaging and the Electronic Age Color Science Color Gamuts & Color Spaces for User Interaction Lecture #7 September 15, 2015 Donald P. Greenberg

2 Chromaticity Diagram

3 The luminance or lightness axis, when added to the chromaticity diagrams provides the third dimension for color.

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6 3D Model - Billmeyer

7 Color Demonstration Video (Jeremy Selan Color Cube Demo)

8 Trichromatic Generalization Many colors can be matched by additive mixtures of suitable amounts of three fixed primary colors. Others have to be mixed with a suitable amount of one before it can be matched by the other two. All the colors can be matched in one of these two ways: The restriction is that none of the primary colors can be matched by an additive mixture of the other two.

9 Color Gamuts

10 Trichromatic Generalization Many colors can be matched by additive mixtures of suitable amounts of three fixed primary colors. Others have to be mixed with a suitable amount of one before it can be matched by the other two. All the colors can be matched in one of these two ways: The restriction is that none of the primary colors can be matched by an additive mixture of the other two.

11 Chromaticity Diagram & Gamut (monitors) Dominant Hue

12 Chromaticity Diagram & Gamut (monitors).. Nearest Color

13 Chromaticity Diagram & Gamut (printers)

14 Sharp 4 Color Display

15 Sharp 4 Color Display

16 Sharp 5 Color Display Kit Eaton. Sharp s New Five Color LCD Displays 99% of Visible Colors, But Not on Your TV, Fast Company, May 29, 2009http://

17 Sharp 5 Color Display

18 5 Color Gamut Color coordinates and gamut for five-primary LCDs. Hui-Chuan Cheng, Linghui Rao, Shin-Tson Wu. Color Breakup Suppression in Field-Sequential Five-Primary-Color LCDs, Jourrnal of Display Technology, June 2010.

19 Expanded colar gamut reproduced by sixprimary projection display

20 Expanded color gamut reproduced by sixprimary projection display

21 Color Space Diagram with Various Gamuts

22 How do you map a color which is outside the gamut of a display with four or five primaries? How do you map a color which is inside the gamut? Which and how many primaries do you use and why?

23 Color Spaces for User Interaction RGB Cube Hexacone Model Munsell Color System HSL Biconical Solid (Hue, Saturation, Lightness) Others

24 RGB Cube B Blue Cyan Magenta White Black Green G R Red Yellow

25 Hexacone Model

26 Hexacone Model

27 Perceptually Uniform Color Spaces Chromaticity specifies the basic color (hue) of an object. Comparing chromaticities gives the best indicator of the color differences between two objects. A chromaticity diagram where equal physical distances (on the diagram) indicate equal perceptual differences would be useful. Why?

28 MacAdam Experiments Subjects were shown colors of known chromaticity (luminance was held constant) and were asked to match the sample using an adjustable color source. Each chromaticity point studied is surrounded by an ellipse proportional in size to the standard deviation of the difference between the actual and match chromaticities. The ellipse indicate how rapidly the color change is perceived.

29 Just Noticeable Differences (JND s) MacAdam Ellipses Note the varying size and orientation of the ellipses. Donald P. Greenberg - Cornell Program of Computer Graphics

30 MacAdam Ellipses - Nonlinear Color Spaces (uvw) u 6y 2x x 1.5 v 6y 3y x 1.5 Basis for the CIELUV and CIELab systems

31 Munsell Color System

32 Munsell Color System Billmeyer

33 Munsell Color System Meyer

34 Munsell Color System Meyer

35 Munsell Color System Meyer

36 Biconical Color Solid George Joblove

37 Biconical Color Solid George Joblove

38 Biconical Color Solid George Joblove

39 Color Constancy The eye has evolved to see the world in unchanging colors, regardless of shifting and uneven illumination. The fact remains that objects retain their color identity under a great variety of lighting conditions. -Edwin Land, Scientific American 1977

40 Color Constancy The most deeply shadowed regions of the church s white siding project luminances to the eye almost equal to the luminances projected by the black shingles is the direct sunlight. Yet they look very different. - Irvin Rock. PERCEPTION, 1984 Scientific American Books, Inc., p.22.

41 Color Constancy

42 Color Constancy

43 End...