Notes on Colour...

Colour is said to have three dimensions; hue, value and intensity.
Hue refers to the basic name of the colour (red, orange, yellow  etc)
Value, brightness or luminosity is the lightness or darkness of the colour.  This corresponds to the scale of greys between black and white.
Intensity or chroma refers to the purity, brilliance or saturation of the colour.
Colour intensity is reduced by adding white or the complimentary colour.

Tint refers to a lighter than normal value of a colour (pink, baby blue, aqua etc)
Shade refers to a darker than normal value of a colour (deep purple, forest green etc)
Tones are colours modified by white or their complimentary colours.

The Spectrum
When a beam of light passes through a prism it is diffracted or spread out into the spectrum which we see as the colours of the rainbow. 

In the 15th century, Leonardo da Vinci identified four primary colours: red, yellow, green and blue which are the colours we see most easily in the rainbow.   These colours are sometimes referred to as psychological primaries because their significance is based on how colour is perceived rather than on the physical characteristics of light.
These are also the colours traditionally used in school houses or teams.

In 1666, Sir Isaac Newton named seven spectral zones:  red, orange, yellow, green, blue, indigo and purple each of which have a different, measurable wavelength.  The longest wavelength of visible light is red and the shortest is blue.  Newton’s colour divisions are scientifically based and are still taught today sometimes by using the mnemonic, “Richard of York gave battle in vain”.
[Newton also connected the different colours or wavelengths to the seven musical notes of the diatonic scale (C – red; D – orange; E - yellow and so on) and with the seven “heavenly spheres”, the planets of our solar system plus the sun and the moon but excluding Earth.]

Although the colours of the spectrum are all part of natural sunlight, the relative proportions of the colours are variable.  Standard white light only exists at midday:  this is when the colours are seen at their truest and the shadows are black.  In the early morning and late afternoon when the sun is low, blue frequencies are filtered out by the air and the light is more red and yellow - warm and glowing and the shadows are blue.  At dawn or dusk, colours are more muted and seem nearer to shades of grey and objects don’t cast shadows.  Moonlight, reflected sunlight, gives an other-worldly feel to colours which is heightened by the shadows it produces. 

The Colour Wheel
We are taught the three primary colours; red, yellow and blue are used as starting points when making a colour wheel.  These three colours are generally the colours identified by da Vinci but ignoring the green.  A more accurate colour wheel can be made by using magenta, yellow and cyan, the colours used in printing.

Colour accuracy is achieved by careful observation. Only by observing and getting to know a subject visually, can we start to depict it or intentionally distort it.     

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