colour theory helge seetzen university of british columbia [email protected]...
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Colour Theory
Helge SeetzenUniversity of British Columbia
Presentation and Outline athttp:\www.sunnybrooktech.com\colour.html
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Colour Theory
Artist: Colour is a property of objects!
Physicist: Colour is a property of light!
Psychology: Colour is a property of our vision!
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The Physicist: The Lightpipe
LED Array
Input Window
Optical LightingFilm
Mirrored Endcap
Ext
ract
or
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• 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
The Artist: The Colour Wheel
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• wave?
• particle?
• ray?
The Physicist: What is Light?
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Wavelength - distance from peak to peak, or trough to trough
Frequency - cycles per second; how many peaks pass a given point in 1 second
The Physicist: Defining a Wave
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The Physicist: Visible Spectrum
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Mixing colours created by light.- Video Cameras- Computer Screens- Television Lights- Video Monitors
Primary Colours- Red- Green- Blue
The Physicist: Additive Colours
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Additive Colours
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The Physicist: But…
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• Used for mixing inks for printing.
• Primary colors are:- Yellow- Cyan- Magenta
Subtractive Colours
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The Physicist: Subtractive Colours
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The Psychologist: And the Eye?
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The Psychologist: And the Eye?
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The Psychologist: Cone Sensitivity
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Perception of monochromatic lightof a laser at 640 nm
The Psychologist: An Example
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640 photons
The Psychologist: Incoming Light
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Red cone is stimulated more than green cone
The Psychologist: Stimulation
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We have a perception of red
The Psychologist: Perception
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Perception of yellow light
The Psychologist: Trickier Case
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The Psychologist: Incoming Light
Incoming light of 560-580nm
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Red and green cone are stimulated equally
The Psychologist: Stimulation
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We have a perception of yellow
The Psychologist: Perception
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Colour: Bringing it all together
0
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Wavelength(nm)
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Wavelength(nm)
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Intensity
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Colour: Bringing it all together
Integration of each cone signal
5.51.50.3
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Wavelength(nm)
Cone
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Stim
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Wavelength(nm)
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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.