cs781 - Colour for Computer Graphics - Winter 2012

Course Notes

Lecture 7 - Creating Colour with a Computer

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Self-Luminous Devices

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

Colour CRT

Monochrome CRT

What is it?

How is an image created?

What light is emitted?

Colour CRT

What is it?

What light is emitted?


Calibrating a Colour CRT

The Video 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?

The Colour Output of a CRT

The colour gamut

The colour cube

The colour cube in colour space

The colour cube in chromaticity coordinates

Potential Problems

Colour LCD

These are widely used because they occupy little volume, use little energy, and weigh little compared to CRTs. Their colour performance is comparable to CRTs, but the structure of the images they produce can be intrusive

Technological basis

What if we had four filters?

Colour OLED

Solid state photodetectors and LEDs are very closely related

Plasma Display Panel (PDP)

Fuorescent Lights

They consist of

  1. A gas tube coated on the inside with a phosphor.
  2. It is filled mostly with inert gases, to which a small amount of mercury vapour is added.
  3. Electrodes at each end of the tube

They make light by

PDPs

A PDP is an array of electrodes and phosphors which, in the off state maintain a gas just below it breakdown level.

Fluorescent light is turned off and on by applying varying voltages to the electrodes.

Thus, a PDP is in effect an array of tiny fluorescent lamps..

Field Effect Display (FED)

Just as the PDP is an array of tiny fluorescent lamps, an FED is an array of tiny CRTs.


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