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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
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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
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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
- He came up with the colour wheel aka colour circle in the form of a Newton Disc (Disappearing Colour Disc)
- 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.