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C o l o u r Theory

This presentation explores colour theory from the perspectives of physics, art, and psychology, covering topics such as additive and subtractive colours, cone sensitivity, and the integration of colour signals. Gain a comprehensive understanding of colour and its impact on our perception.

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C o l o u r Theory

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  1. Colour Theory Helge Seetzen University of British Columbia helge.seetzen@sunnybrooktech.com Presentation and Outline at http:\www.sunnybrooktech.com\colour.html

  2. Colour Theory Artist: Colour is a property of objects! Physicist: Colour is a property of light! Psychology: Colour is a property of our vision!

  3. The Physicist: The Lightpipe Mirrored Endcap Extractor Optical Lighting Film Input Window LED Array

  4. The Artist: The Colour Wheel • A colour circle, based on red, yellow and blue, is traditional in the field of art and is a way of arranging colours to show a variety of relationships between colours • Sir Isaac Newton developed the first circular diagram of colours in 1666

  5. The Physicist: What is Light? • wave? • particle? • ray?

  6. The Physicist: Defining a Wave Wavelength - distance from peak to peak, or trough to trough Frequency - cycles per second; how many peaks pass a given point in 1 second

  7. The Physicist: Visible Spectrum

  8. The Physicist: Additive Colours Mixing colours created by light. - Video Cameras - Computer Screens - Television Lights • Video Monitors Primary Colours - Red - Green - Blue

  9. Additive Colours

  10. The Physicist: But…

  11. Subtractive Colours • Used for mixing inks for printing. • Primary colors are: • - Yellow • - Cyan • - Magenta

  12. The Physicist: Subtractive Colours

  13. The Psychologist: And the Eye?

  14. The Psychologist: And the Eye?

  15. The Psychologist: Cone Sensitivity

  16. The Psychologist: An Example Perception of monochromatic light of a laser at 640 nm

  17. The Psychologist: Incoming Light 640 photons

  18. The Psychologist: Stimulation Red cone is stimulated more than green cone

  19. The Psychologist: Perception We have a perception of red

  20. The Psychologist: Trickier Case Perception of yellow light

  21. The Psychologist: Incoming Light Incoming light of 560-580nm

  22. The Psychologist: Stimulation Red and green cone are stimulated equally

  23. The Psychologist: Perception We have a perception of yellow

  24. = Colour: Bringing it all together

  25. = Colour: Bringing it all together 5.5 1.5 0.3 Integration of each cone signal

  26. Colour: There is a lot more to it! The ‘primary colours’ are A, B, and C. Then for a given real color, its components with respect to the primaries are as follows: x = A/(A+B+C)y = B/(A+B+C)z = C/(A+B+C) with x + y + z = 1 The CIE diagram is a plot of X vs. Y for all visible colors.

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