COLOUR PERCEPTION

The phenomena that have an impact on how our brains perceive colours are:

• Colour constancy
• Simultaneous contrast
• Optical mixture
• Spatial dimension

Colour constancy

Colour constancy involves our tendency to compensate for the effect of various light sources on the colour of the objects we see. For example, a company's logo is illuminated by different light sources in different locations. For each viewing situation, a camera would register dramatic shifts in the logo's colour because of the various light sources. However, our brains rapidly compensate for each situation, and we perceive the colour of the logo as the same in all the cases.

Simultaneous contrast

When two complementary colours are placed side, it tends to heighten each others saturation and brilliance without an apparent change in hue. Simultaneous contrast in hue is most easily perceived when two colours are fairly uniform in value. If one colour is much lighter or darker than the other, the effects of contrasting values become more noticeable. Simultaneous contrast also affects the apparent value of a colour, which can be made to appear  lighter or darker according to the value of its background colour. Surrounding colours with black tends to make them richer and more vibrant, while outlining with white often has the opposite effect.

Optical mixture

Optical mixture is the opposite of simultaneous contrast. When an object's patches of colour are so small that they pass below the threshold of conscious perception, we see the colours as optically mixed.

Spatial dimension

Spatial dimension, the fourth of these internal phenomena, occurs when our brain add or subtract distance, depending upon the colours perceived. We tend to perceive warmcoloured objects, for example red, orange, and yellow, closer than cool-coloured ones, such as green, blue and purple.

The simplest type, such as the Brewster or prang colour wheel, organizes colour pigments into primary, secondary, and tertiary hues.