COP Lecture Series: Colour Theory - Systematic Colour

Part one.
Systematic Colour.

Three area which can relate to how we see colour:
- physical
- physiological
- psychological

Spectral colour - colour that is evoked by a single wavelength of light in a visible spectrum. This single wavelength generates monochromatic light.
Every wavelength is perceived as a spectral colour in a continuous spectrum.
The colours of similar or sufficiently close wavelengths are often indistinguishable by the human eye.

Colour is based on light - each colour has a different wavelength.
White light hits something physical and splits into colour - travels at different wavelengths and speeds, eg. red produces longer wavelengths and purple, shorter wavelengths.

Our perception of any colour is based on the eye receiving light which has been reflected from a surface or object.
White takes on the colour around it, whereas black absorbs more light so retains more of its colour. The colour of the surface will also affect a colour.
For example, the sky is pure white light - wavelengths bouncing off everything produce its colour, such as particles/ shorter and longer wavelengths, such as sunsets/ the sky has no colour.

The eye contains two kinds of receptors:
RODS - convey shades of black, white and grey.
CONES - allow the brain to perceive colour.

There are three types of cones:
1. sensitive to red-orange light.
2. sensitive to green light.
3. sensitive to blue-violet light.

When a single cone is stimulated, the brain perceives the corresponding colour.
If our green cones are stimulated, we see 'green'/ if our red-orange cones are stimulated, we see red'/ if both our green and red-orange cones are simultaneously stimulated, our perception is 'yellow' - Yellow does not exist as a colour.
Because of this physiological response, the eye can be 'fooled' into seeing the full range of visible colours through the proportionate adjustment of just three colours: red, green and blue.
The way we perceive colour can be affected by different physiological aspects, for example, colour blindness.

Part two.
The Principles of Colour.

Josef Albers (1888 - 1976)
Johannes Itten (1888 - 1967)

Colour - pigment - media.
Primary - secondary - tertiary.

Mixing primary, secondary and tertiary colours eventually cancel each other's wavelengths out and the colour becomes a neutral grey.

Spectral colour - the eye cannot differentiate between spectral yellow and some combination of red and green. The same effect accounts for our perception of cyan, magenta and other in-between spectral colours.
Colour modes: RGB - screen based colour (additive)/ CMYK - print based colour (subtractive).
The primaries of RGB provide secondaries of CMYK.

Part three.
Dimensions of Colour.

Chromatic value = hue + tone (luminance) + saturation.
Luminance (shade)
- how much light does it reflect?
- tint - adding more white.
- tone - adding white/ dark.
Saturation
- amount of colour we see.

Conclusion: we always see colour in relation to something else. The Pantone colour matching system can help with this in reproducing exact colours for design work.