Colour Theory

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Colour Theory
Helge Seetzen University of British
Columbia helge.seetzen_at_sunnybrooktech.com Present
ation and Outline at http\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
Mirrored Endcap
Extractor
Optical Lighting Film
Input Window
LED Array
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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

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The Physicist What is Light?

• wave?

• particle?

• ray?

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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
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The Physicist Visible Spectrum
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The Physicist Additive Colours

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

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Additive Colours
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The Physicist But
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Subtractive Colours

• Used for mixing inks for printing.
• Primary colors are
• - Yellow
• - Cyan
• - Magenta

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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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The Psychologist An Example
Perception of monochromatic light of a laser at
640 nm
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The Psychologist Incoming Light
640 photons
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The Psychologist Stimulation
Red cone is stimulated more than green cone
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The Psychologist Perception
We have a perception of red
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The Psychologist Trickier Case
Perception of yellow light
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The Psychologist Incoming Light
Incoming light of 560-580nm
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The Psychologist Stimulation
Red and green cone are stimulated equally
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The Psychologist Perception
We have a perception of yellow
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Colour Bringing it all together
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Colour Bringing it all together
5.5 1.5 0.3
Integration of each cone signal
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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/(ABC)y B/(ABC)z C/(ABC) with x y
z 1 The CIE diagram is a plot of X vs. Y
for all visible colors.