Colour Theory

Properties

• Perceived Properties - Hue, Colourfulness (Saturation), Luminance
• Mixing - Additive / Subtractive - Primary and Secondary Colours
  • Metamerism
• Complementary colours produce a high level of contrast - this is used in art
• Warm and Cool Colours
• Impossible Colours

Practice

• Colour Schemes - mixing tactics - for aesthetics or for practical
  • Triadic, Monochromatic (single colour), Split complementary, Achromatic/Near Neutrals/Neutrals, Tetradic, Polychromatic, Colourmaps
  • Data visualization - uses a ordered colour set
    • Schemes: see Wiki
    • Representation Methods: continuous, discrete, categorical.
• Colour Gradient - Specifies a range of position-dependent colours, usually used to fill a region
  • Aka Colour Ramp or Colour Progression. In assigning colours to a set of values, it is a continuous colourmap, a colour scheme representation method.

Rough Work here

• HSV, HSL, HSB

• CMYK has a slight deficiency notably in orange and slightly in purples - wider range of colours by adding other colours, like pantone hexachrome (CMYKOG) - discontinued

• spot colours (generated by ink printed using a single run; the standard CMYK colours in offset printing/CMYKOG; technicians prefer to use the name for non-standard offset inks like metallic, fluorescent, or custom hand-mixed inks) (contrast with process colours - CMYK, dots)

  • Pantone is the main spot colour printing system in US and Europe. Others exist too (Wiki)
  • used in offset printing (trans) - lithography (planographic method of printing, based on immiscibility of oil and water)
    • offset printing and lithography are planographic printing processes.
• Types of printing

Evolution

• Newton's Experiments on Colours.
  • He came up with the colour wheel aka colour circle in the form of a Newton Disc (Disappearing Colour Disc)
    • Colour circle is used for, among other purposes for additive colour mixing. Sometimes, adding two colours from different parts of the spectrum might produce a third colour that looks like a light from another part of the spectrum. This type of colour mixing is called metameric matching - metamerism.
  • He gave the first method of mixing, which is to 1. mark two colours in a colour wheel, 2. find their barycenter, 3. Then the distance from the center to the barycenter determines the saturation, while the azimuthal position (the position of the radial line through the barycenter) determines it's hue.
  • Criticized by: Robert Hooke, assistant of Robert Boyle
• Johan Wolfgang von Goethe, a German poet, proposed his set of complementary colours.
• Thomas Young's Trichromatic Theory of Colours. It distinguished additive and subtractive colours. He came up with a colour triangle (also used in CIE 1931 Colour Space)
• Hermann von Helmholtz developed Young's theory by classifying the photoreceptor cells.
• Helmholtz's influence of unconscious inferences.
• James Clark Maxwell's Mathematical description of Young-Helmholtz Trichromatic theory using linear algebra.
• Ewald Hering's Opponent Processes was in dispute with the theory by Young, Helmholtz and Maxwell
• Later, Johannes von Kries published the zone theory in 1905 that synthesizes both descriptions as one, where Young-Helmholtz theory describes the interaction of light with the receptors and Hering the image processing stage.
• In 1925, Erwin Schrodinger published a paper inspired by von Kries, titled 'On the relation of the four color to the three color theory' where he probes for a formal relationship between the two theories.
• The conundrum was solved by the discovery of color-opponent gangelion cells in the retina and lateral geniculate nucleus. We know know the human eye possesses three types of color-sensitive receptors which then combine their signals in three color-opponent channels as proposed by Hering. Thus both theories are correct.