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Boutet's 7-colour and 12-colour colour circles from 1708.
An 1895 mechanical colour wheel, used for experiments with colour vision

A colour wheel or colour circle is an organization of colour hues around a circle, showing relationships between colours considered to be primary colours, secondary colours, complementary colours, etc.

Artists typically use red, yellow, and blue primaries (RYB color model), so these are arranged at three equally-spaced points around their colour wheel.1 Printers and others who use modern subtractive colour methods and terminology use magenta, yellow, and cyan as subtractive primaries.

Colour scientists and psychologists often use additive primaries, such as red, green, and blue, and often refer to their arrangement around a circle as a colour circle, as opposed to a colour wheel.2

The arrangement of colours around the colour circle is often considered to be in correspondence with the wavelengths of light, as opposed to hues, in accord with the original colour circle of Isaac Newton. Modern colour circles include the purples, however, between red and violet.3

Intermediate and interior points of colour wheels and circles represent colour mixtures. In a paint or subtractive colour wheel, the center is usually (but not always4) black, representing all colours of light being absorbed; in a colour circle, on the other hand, the center is white or gray, indicating a mixture of different wavelengths of light (all wavelengths, or two complementary colours, for example).

Some sources use the terms colour wheel and colour circle interchangeably,56 though the one term or the other may be more prevalent in certain fields or certain versions as mentioned above. Some reserve the term colour wheel for mechanical rotating devices, such as colour tops or filter wheels. Others classify various colour wheels as colour disc, colour chart, and colour scale varieties.7

Newton's colour circle, showing the colours correlated with musical notes and symbols for the planets.
A 1904 colour wheel based on red/yellow/blue primaries, and orange/green/violet secondaries

Contents

History

An in-depth history of the colour circles, wheels, spirals, triangles, charts, and other order systems has been published, as a chapter of an e-book, by Sarah Lowengard, focusing on the eighteenth century.8

Colours of the colour wheel

Goethe's colour wheel from his 1810 Theory of Colours

Typical artists' paint or pigment primary colours are blue, red, and yellow. The corresponding secondary colours are green, orange & violet. The tertiary colours are red–orange, red–violet, yellow–orange, yellow–green, blue–violet and blue–green.

A colour wheel based on RGB (red, green, blue) or RGV (red, green, violet) additive primaries has cyan, magenta, and yellow secondaries (cyan was previously known as cyan blue). Alternatively, the same arrangement of colours around a circle can be described as based on cyan, magenta, and yellow subtractive primaries, with red, green, and blue (or violet) being secondaries.

Most colour wheels are based on three primary colours, three secondary colours, and the six intermediates formed by mixing a primary with a secondary, known as tertiary colours, for a total of 12 main divisions; some add more intermediates, for 24 named colours. Other colour wheels, however, are based on the four opponent colours, and may have four or eight main colours.

Goethe's Theory of Colours provided the first systematic study of the physiological effects of colour (1810). His observations on the effect of opposed colours led him to a symmetric arrangement of his colour wheel, "for the colours diametrically opposed to each other… are those which reciprocally evoke each other in the eye." (Goethe, Theory of Colours, 1810 9). In this, he anticipated Ewald Hering's opponent color theory (1872) 10.

The colour circle and colour vision

A colour circle based on additive combinations of the light spectrum, after Schiffman (1990)

A colour circle based on spectral wavelengths will appear with red at one end of the spectrum and violet at the other, and with a wedge-shaped gap representing colours which have no unique spectral frequency; these extra-spectral colours, the purples, are rather formed by the additive mixture of colours from the two ends of the spectrum.

In normal human vision, wavelengths of between about 400 nm and 700 nm are represented by this incomplete circle, with the longer wavelengths equating to the red end of the spectrum. Complements are located directly opposite each other on this wheel. These complements are not identical to those in pigment mixing (such as are used in paint), but when lights are additively mixed in the correct proportions will appear as a neutral grey or white.11

A 1908 colour wheel with red, green, and violet "plus colours" and magenta, yellow, and cyan blue "minus colours"
A 1917 four-way colour circle related to the colour opponent process

The colour circle is used for, among other purposes, illustrating additive colour mixture. Combining two coloured lights from different parts of the spectrum may produce a third colour that appears like a light from another part of the spectrum, even though dissimilar wavelengths are involved. This type of colour matching is known as metameric matching.12 Thus a combination of green and red light might produce a colour close to yellow in apparent hue. The newly-formed colour lies between the two original colours on the colour circle, but they are usually represented as being joined by a straight line on the circle, the location of the new colour closer to the (white) centre of the circle indicating that the resulting hue is less saturated (i.e., paler) than either of the two source colours. The combination of any two colours in this way will always be less saturated than the two pure spectral colours individually.

Objects may be viewed under a variety of different lighting conditions. The human visual system is able to adapt to these differences by chromatic adaptation. This aspect of the visual system is relatively easy to mislead, and optical illusions relating to colour are therefore a common phenomenon. The colour circle is a useful tool for examining these illusions.

The display of colours using spectral colours around a circle in order to predict the admixture of light can be traced to work by Sir Isaac Newton. The psychophysical theory behind the colour circle dates to the early colour triangle of Thomas Young, whose work was later extended by James Clerk Maxwell and Hermann von Helmholtz). Young postulated that the eye contains receptors that respond to three different primary sensations, or spectra of light. As Maxwell showed, all hues, but not all colours, can be created from three primary colours such as red, green, and blue, if they are mixed in the right proportions. The Young–Helmholtz theory is still seen as the most effective in modeling human colour vision,citation needed though the colour vision system is far more complex than differences in the retina alone, with different cells in the lateral geniculate nucleus also responding in opponent fashion to complementary colours, and further colour coding occurs in the visual cortex.13

Colour wheels and paint colour mixing

There is no straight-line relationship between the colours mixed in pigment, which will vary from medium to medium. Whereas with a psychophysical colour circle, the resulting hue of any mixture of two coloured light sources can be determined simply by the relative brightness and wavelength of the two lights12, a similar calculation cannot be performed with two paints. As such, a painter's colour wheel is indicative rather than predictive, being used to compare existing colours rather than calculate exact colours of mixtures. Because of differences relating to the medium, different colour wheels may be created according to the type of paint or other medium used, and many artists develop their own individual colour wheels. These will often contain only blocks of colour rather than the gradation between tones which is characteristic of the colour circle.14

Colour wheel software

A number of interactive colour wheel applications are available both on the internet and as desktop applications. These programs are used by artists and designers to simplify the task of picking matching colours for a design.

Colour schemes

Main article: Colour scheme

Colour schemes are logical combinations of colours on the colour wheel.

In colour theory, a colour scheme is the choice of colours used in design for a range of media. For example, the use of a white background with black text is an example of a basic and commonly default colour scheme in web design.

Colour schemes are used to create style and appeal. Colours that create an aesthetic feeling when used together will commonly accompany each other in colour schemes. A basic colour scheme will use two colours that look appealing together. More advanced colour schemes involve several colours in combination, usually based around a single colour; for example, text with such colours as red, yellow, orange and light blue arranged together on a black background in a magazine article.

Colour schemes can also contain different shades of a single colour; for example, a colour scheme that mixes different shades of green, ranging from very light (almost white) to very dark.

See also

Wilhelm von Bezold's 1874 Farbentafel

References

  1. ^ Kathleen Lochen Staiger (2006). The Oil Painting Course You've Always Wanted: Guided Lessons for Beginners. Watson–Guptill. ISBN 0823032590. 
  2. ^ Linda Leal (1994). The Essentials of Psychology. Research & Education Assoc. ISBN 0878919309. 
  3. ^ Steven K. Shevell (2003). The Science of Color. Elsevier. ISBN 0444512519. 
  4. ^ Martha Gill (2000). Color Harmony Pastels: A Guidebook for Creating Great Color Combinations. Rockport Publishers. ISBN 1564967204. 
  5. ^ Simon Jennings (2003). Artist's Color Manual: The Complete Guide to Working With Color. Chronicle Books. ISBN 081184143X. 
  6. ^ Faber Birren (1934). Color Dimensions: Creating New Principles of Color Harmony and a Practical Equation in Color Definition. Chicago: The Crimson Press. ISBN 1428651799. 
  7. ^ Joseph Anthony Gillet and William James Rolfe (1881). Elements of Natural Philosophy: For the Use of Schools and Academies. New York: Potter, Ainsworth. 
  8. ^ Sarah Lowengard (2008). The Creation of Color in Eighteenth-Century Europe. Columbia University Press. 
  9. ^ Goethe, Johann (1810). Theory of Colours, paragraph #50. 
  10. ^ Goethe's Color Theory
  11. ^ Krech, D., Crutchfield, R.S., Livson, N., Wilson, W.A. jr., Parducci, A. (1982) Elements of psychology (4th ed.). New York: Alfred A. Knopf. pp. 108-109.
  12. ^ a b Schiffman, H.R. (1990) Sensation and perception: An integrated approach (3rd ed.). New York: John Wiley & Sons, pp. 252-253.
  13. ^ Carlson, N.R. (1981) Physiology of behavior (2nd ed.). Boston, MA: Allyn and Bacon. pp. 247–250.
  14. ^ Rodwell, J. (1987) The complete watercolour artist. London: Paul Press, pp. 94-95.

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