2. Color CS5540 HCI Rich Riesenfeld Fall 2011 Lecture Set 25 Fall 20111

3. 2 Color Issues Physical nature of colorPhysical nature of color Eye mechanism of colorEye mechanism of color –Rods, Cones, tri-stimulus model Brain mechanism of colorBrain mechanism of color Color spacesColor spaces Aesthetic and physiologicalAesthetic and physiological

4. 3 Color Color is complicated!Color is complicated! –Highly nonlinear –No singular model to explain all Many simplistic models, explanationsMany simplistic models, explanations Many mythsMany myths Much new knowledgeMuch new knowledge

5. 4 Color Many phenomena to explainMany phenomena to explain –High light / low light –Illusions –Color blindness –Metamers

6. 5 Additive Primary Colors (1,0,1) magenta (0,0,1) blue (0,1,0) (0,1,1) cyan green (1,0,0) red (1,1,0) yellow

7. 6 Additive Primary Colors (0,1,0) green (1,0,0) red (1,1,0) yellow

8. Fall 20117 Additive Primary Colors (1,0,1) magenta (0,0,1) blue (1,0,0) red

9. Fall 20118 Subtractive Primary Colors (1,0,1) magenta (0,0,1) blue (1,1,0) yellow (0,1,0) green (1,0,0)red (0,1,1) cyan

10. Fall 20119 Additive Primary Colors (0,0,1) blue (0,1,0) (0,1,1) cyan green

11. Fall 201110 Subtractive Primary Colors (1,0,1) magenta (1,1,0) yellow (1,0,0)red

12. Fall 201111 Subtractive Primary Colors (0,1,0) (0,1,1) cyan green (1,1,0) yellow

13. Fall 201112 Subtractive Primary Colors (1,0,1) magenta (0,0,1) blue (0,1,1) cyan

14. 13 Wavelength Spectrum infrared light ultraviolet light Wavelength (nm) 700 600 500 400 Seen in physics, physical phenomena (rainbows, prisms, etc)Seen in physics, physical phenomena (rainbows, prisms, etc) 1 Dimensional color space1 Dimensional color space

15. Fall 201114 Wavelength Spectrum

16. 15 Color Space “Navigating,” moving around in a color space, is tricky“Navigating,” moving around in a color space, is tricky Many representations (spaces) for all colorsMany representations (spaces) for all colors Can you get to a nearby color? Can you predictably adjust a color?Can you get to a nearby color? Can you predictably adjust a color?

17. Fall 201116 Color Cube (0,0,0) (0,1,0) (0,1,1) (1,0,1) (0,0,1) (1,0,0) (1,1,0) blue cyan white (1,1,1) black green yellow magenta red gray

18. Fall 201117 Color Cube (0,1,0) (0,1,1) (1,0,1) (0,0,1) (1,0,0) (1,1,0) blue cyan white (1,1,1) green yellow magenta red

19. Fall 201118 Complementary Colors Add to Gray (0,1,1) (1,0,1) (0,0,1) (1,0,0) (1,1,0) blue cyan white (1,1,1) yellow magenta red (0,1,0) green

20. Fall 201119 Complementary Colors Looking at color cube along major diagonal

21. 20 (H, S,V) Color Space Hue: ColorHue: Color –Chroma Saturation: Strength of a colorSaturation: Strength of a color –Neutral gray has 0 saturation Brightness/Value: Intensity of light emanating from imageBrightness/Value: Intensity of light emanating from image

22. Fall 201121 The hue of an object may be blue, but the terms light and dark distinguish the brightness of one object from another. (Hue, Saturation, Value/Intensity) (H, S,V) Color Space

23. 22 Saturation

24. Fall 201123 Other HSX Color Spaces (Cones) 0.0 cyan white1.0 yellow magenta red 120 ˚ green black 0˚0˚ V 240 ˚ blue S H

25. Another HSX Color Space (double cone) 0.0 cyan white 1.0 magenta red black 0˚0˚ S L H 240 ˚ blue green 120 ˚ yellow 24 Fall 201124

26. 25 Tristimulus Color Theory Any color can be “matched” by a mixture of three fixed base colors (primaries)Any color can be “matched” by a mixture of three fixed base colors (primaries) Eye has three kinds of color receptors called conesEye has three kinds of color receptors called cones Eye also has rods (low light receptors)Eye also has rods (low light receptors)

27. Fall 201126 Color Receptors in Eye Red, Green, Blue Long, Medium, Short

28. Fall 201127 Color Receptors in Eye

29. Fall 201128 Wavelength Spectrum infrared light ultraviolet light Wavelength (nm) 700 600 500 400

30. 29 Why are runway lights blue?Why are runway lights blue? Why are console lights green?Why are console lights green? Why color is the Kodak box?Why color is the Kodak box? Color Response - 1

31. 30 What color is the Kodak box? Color Response - 2 (nm) 700 600 500 400 555

32. 31 Color Matching Experiments Given a reference color, try to match it identicallyGiven a reference color, try to match it identically What does “negative red,” or “negative color” mean??What does “negative red,” or “negative color” mean??

33. 32 CIE Color Space ( X, Y, Z ) represents an imaginary basis that does not correspond to what we see Define the normalized coordinates: x = X / ( X + Y + Z ) y = Y / ( X + Y + Z ) z = Z / ( X + Y + Z )

34. 33 CIE Color Space x = X / ( X + Y + Z ) y = Y / ( X + Y + Z ) z = Z / ( X + Y + Z ) x + y + z = 1

35. Fall 201134 Color Gamuts: CIE Color Chart

36. Fall 201135 Color Gamuts: CIE Color Chart

37. Fall 201136 Color Gamuts: CIE Color Chart www.cs.rit.edu/~ncs/color/a_chroma.html

38. 37 Color Applets www.cs.brown.edu/exploratories/freeSoftware/repository/ edu/brown/cs/exploratories/applets/combinedColorMixing /combined_color_mixing_java_browser.html www.cs.brown.edu/exploratories/freeSoftware/repository/ edu/brown/cs/exploratories/applets/combinedColorMixing /combined_color_mixing_java_browser.html http://www.cs.brown.edu/exploratories/freeSoftware /repository/edu/brown/cs/exploratories/applets/comb inedColorMixing/combined_color_mixing_java_plu gin.html http://www.cs.brown.edu/exploratories/freeSoftware /repository/edu/brown/cs/exploratories/applets/comb inedColorMixing/combined_color_mixing_java_plu gin.html

39. Fall 201138 Another Space

40. 39 Important Concepts AdaptationAdaptation –Slow process ConstancyConstancy –Immediate process

41. Fall 201140 Output to the Brain from Eye R G B + + + - + - B B - RGR-GRGR-G B R G YY YY

42. Fall 201141 Mechanism + + + + + + + + + - - - + + + - - - + + + - - - + + + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

43. 42 Lecture Set 25 Fall 201142

44. Fall 201143 Color Receptors in Eye Red, Green, BlueRed, Green, Blue Long, Medium, Short

45. 44 Saturation