CS781 - Colour for Computer Graphics - Winter 2009

Lecture 14

Creating Colour: Self-Luminous Devices

`Self-luminous' means producing light without an external illuminant.

Colour CRT

Calibrating a Colour CRT

Calibration

Characterization

Modelling a Colour CRT

The colour gamut

The colour cube

The colour cube in colour space

The colour cube in chromaticity coordinates

Measuring the Colour of CRT Output

Geometry

Problems

Building a Mapping for XYZ input

Model-based

Forward

  1. X = A Ii(vi) + Black
  2. Ii(v) = Gi f(vi)
  3. f(vi) = vi^\gamma

Invert

  1. Ii(vi) = invA (X - Black)
  2. fi = Ii(v) / Gi
  3. vi = invf( fi ) = fi^{-\gamma}

Look-up Table Based

Calibrating a Colour CRT

The Television Signal

Viewing Conditions

Reference white

Viewing distance

Surround

The White Axis

Colour of grey (all guns equal: vR = vG = vB) depends on surround

Gamma Correction

What do you want gamma to be?

Colour LCD

Technological basis

What if we had four filters?

Colour OLED

Solid state photodetectors and LEDs are very closely related


Creating Colour: Illuminated Devices

Half-tone Printing

Photography

Continuous-tone Printing


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