VDU colorimetry

1
VDU colorimetry

• Digital input - luminance output
• gamma-correction
• channel interdependence
• local interdependence
• Colour correction matrix
• Hard-copy / soft-copy transformation
• colour management
• cognitive effects

2
Video Display Unit (VDU)

• White point setting differences
• CCT x y
• D50 5000 .346 .359
• D65 6504 .313 .329
• D93 9300 .280 .312

3
VDU monitor

• Input bit streams
• Display processor converting for output device
• Object oriented storage of characters scaling,
  rotation, etc.
• Buffer memory

4
Buffer memory

• Size Number of pixels x Bits in pixel
• 3 bit colour 640 x 400 x 3 bit colour 95
  kbyte(3 bit colour R, G, B on - off)
• 8 bit per colour channel 640 x 400 256 000
  pixels256 000 x 8 x 3 768 kbyte
• Refresh rate 640 x 400 x 3 768 000 bits,70
  frames/sec 54 Mbit/s

5
3 bit colour palette
6
Display processing

• Character generation- ASCII 7 bit code 128
  characters- ISO 8 bit code 256
  characters- Code sheets- Additional
  information - Font colour - Character outline

7
Display processing

• Graphics generation- Graphical user
  interface - Windows - Icons (symbols) - Mouse
  pointer

8
Colour systems

• Basic 8-colour setR, G, B on - off 3 bits per
  character
• Logically defined colours CLUTs
• Dithering- spatial dithering temporal
  dithering

9
Spatial dithering

• 2 x 2 groups 5 luminance levels
• 2 x 2 arrays, 2 bits per pixel
• 28256 arrangements
• 35 colours, 23 chromaticities

10
Colour look-up tables

• Logical and actual colour
• CLUT image as bit-codes per pixel in terms of a
  set of logical colours.

11
Digital-to-Analogue Conversion

• n bit code for primary colour 2n levels
• in CLUT ?-correction possible
• RGB ?HVC conversion
• 8 bit palettes

12
Anti-aliasing

• Anti-aliasing processors Real time interpolation
  in CLUT

13
System structure