Tuesday, July 08, 2008

Hues - a systems perspective

Sir Isaac Newton's colour circle
showing the colours correlated with musical notes and symbols for the planets.


I touched on various systems for analysing colour in Colour - a scientific perspective. This week I'm going to try and cover the systems perspective in terms of:
  • Hues: primary, secondary and tertiary colours
  • How to represent colour relationships in space - how many different ways can you arrange colour relationships in different shapes in space (triangles, wheels and globes)
  • Colour harmonics - complementary colours, analogous colours etc
I have a simple test for deciding whether to look in any depth at any art book which has a section on the colour wheel. If it talks about colour and starts with a notion that there are three primary colours - red, blue and yellow - plus it has a very simple 3 primary, 3 secondary colour wheel then I generally put it down and reach for the next one.

I honestly believe that very many artists have failed to realise their potential because of a poor understanding of colour generated by weak explanations of colour analysis and the colour wheel in art instruction books.

Having said that, where do I go from here to try and remedy those perceived deficiencies? The simple answer is I can't do as good a job as some other people have already done. However, I can introduce some basic concepts for artists and then point people in the direction of key publications which, in my opinion, are a lot more helpful plus some useful websites.

What are primary colours?

In principle, primary colours are the colours you can't make from any other colour. They are also the colours which are used to make all other colours of the spectrum.

Which are the primary colours?

The primary colours partly depends on what sort of mixing and media you're considering - for example:
  • SUBTRACTIVE: in pigments, red, yellow and blue are the historical set of primary colours which create all other colours. In theory mixing all three together creates black.
  • SUBTRACTIVE: in practice - and in printing - the primary colours which must be used with black to produce all other colours are cyan, magenta and yellow
  • ADDITIVE: when mixing lights on a stage or viewing images on a computer screen, the primary colours are red, green and blue. Mixing all three together creates white light.
Note that black and white don't traditionally feature feature in the above despite the fact that they might be used by artists to produce colours.

Secondary colours are what we get if we mix two primaries together. The actual colour depends on the balance within the mix. In principle, Tertiary colours are what result from mixing a primary and a secondary colour.

Wikipedia identifies the following approaches to mixing secondary colours. The section is not properly accredited - but I've seen these mixes cited in a number of different places.

red (●) + green (●) = yellow (●)
green (●) + blue (●) = cyan (●)
blue (●) + red (●) = magenta (●)

cyan (●) + magenta (●) = blue (●)
magenta (●) + yellow (●) = red (●)
yellow (●) + cyan (●) = green (●)

red (●) + yellow (●) = orange (●)
yellow (●) + blue (●) = green (●)
blue (●) + red (●) = violet (●)

Have the primary colours always been the same?

Simple answer is No. What were considered to be primary colours depends on where you lived and which scientist you favoured.

What follows draws on two books and various websites which are part of the information sites (listed at the end). The books are:
At different times, scientists (rather than artists) have all had a different view about what are the primary colours or primary hues. The Wikipedia article on color theory provides a background to the historical development. For example:
  • Plato thought that all colours were derived from black, white, red and yellow (Timaios, 67D-68C in the Stephanus numbering)
  • Aristotle identified hues as being white, black, red, yellow, brown, violet, green and blue
  • Leonardo da Vinci thought that the primary colours were white, yellow, green, blue, red and black
  • Sir Isaac Newton, who discovered the colours of the spectrum and identified hues as being red, orange, yellow, green, blue, indigo and violet (see Optiks)
  • In Theory of Colours (which influenced Turner) Goethe he characterized colour as arising from the dynamic interplay of darkness and light and developed a two dimensional colour wheel based on the triad of red, blue and yellow with secondaries as complementary hues of the primary colours.
  • Otto Runge, a german painter modelled colour as a sphere and used black and white alongside red, blue and yellow
  • Ogden Rood had jsut three primary colours - but these were red, green and blue
  • Munsell focused on perceived colour. He identified five principal hues - red, orange, yellow, green, blue, purple.
There are many other people who've also had other perspectives.
For much of the 19th century artistic color theory either lagged behind scientific understanding or was augmented by science books written for the lay public, in particular Modern Chromatics (1879) by the American physicist Ogden Rood, and early color atlases developed by Albert Munsell (Munsell Book of Color, 1915, see Munsell color system) and Wilhelm Ostwald (Color Atlas, 1919). Major advances were made in the early 20th century by artists teaching or associated with the German Bauhaus, in particular Wassily Kandinsky, Johannes Itten, Faber Birren and Josef Albers, whose writings mix speculation with an empirical or demonstration-based study of color design principles.
Wikipedia - Color Theory
What's the problem with primary colours?

This could be a long and tortuous explanation or it can be fairly simple with an injunction to go and read the science if you don't believe the statement.

The simple facts are that:
  • pigments don't match the theoretical primary colours which create all colour. All pigments tend to lean away from the 'pure' colour which has a specific wavelength.
  • there is no straight line relationship when mixing colours. They vary according to the pigments or chemicals they are based on - which rather tends to complicate the mixing of colours.
  • colour theory for artists doesn't take account of the effect of either the sub-strata or the environment and light on pigment-based media. The reality is that the context in which pigments are used have a very decided impact on the colour seen.
The bottom line is that it isn't actually possible to produce all possible colours from the 'right' choice of pigment based art media. It also isn't possible to guarantee that even if you could, these colours would always look the same in all contexts.

Handprint (who you'll recognise from previous posts in this colour project) has a very useful summary of the different theories about primary colours over time - Do primary colours exist? His conclusion is set out below.
The conclusion of this historical excursion is that "primary" colors are only useful fictions. They are either imaginary variables adopted by mathematical models of color vision, or they are imperfect but economical compromises adopted for specific color mixing purposes with lights, paints, dyes or inks.

Primary colors are sometimes defended as a pedagogical simplification to teach elementary color mixing. But, as I propose elsewhere, there are better frameworks for that purpose, too. "Useful fictions" should be employed only when they are useful.

At bottom, the only justification for primary colors is to minimize the number of components required to mix all colors.
Handprint - Do primary colours exist?
I agree with Bruce that there's an excellent discussion of colour theory and how it developed over time in Colour and Culture by John Gage. Later on in this project I'm going to be highlighting the palettes used by different artists over time.

So much for primary colours!

Next I'll be looking at how different people have tried to organise the visual relationship between different hues. Like primary colours - there's more than one way of looking at this.


The Making A Mark Project on Colour - previous posts

Resources for Artists information sites created by makingamark

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