CS781 - Colour for Computer Graphics - Winter 2009

Lecture 20

Reading Colour

		Categorical	Continuous
		Find the right one among a few. Encoding easy. Resistant to contrast effects	Find the right one among a continuous distribution. Precision falls off with distance. Encoding not easy.
One context	Purely perceptual task	Easy Multiple hits resolvable	Easy Colour matching
Several contexts	Requires memory: almost the definition	Easy Multiple hits not resolvable	Hard

What is a context in this context?

Temporal Context

Simultaneity

Spatial Context

Context can be strengthened

Introducing a colour into another context

As a memory

10 colours
basic perceptions
seven from opponent colours, includes neutral = grey
plus brown, orange, pink, purple
except for orange these names are conventional
orange, from Arabic/Persian narang

As a sample

Object with a known colour
- Compare a remembered represebtation of the object
- Colour attached to object
- 100 colours
- names are mostly names of familiar objects, sometimes modified
  - lime, lime-green
  - olive
  - tan
- for artists the names of pigment are learned
  - vermillion
  - madder
  - cadmium yellow
Physical sample
- 1500 colours
- too many colours for names to work

As a specification

Colour Scales

Dimensions of colour spaces
- Brightness scales
- Saturation scales

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