Audio Visual Design Guidelines

Understanding the System Contrast Ratio

3 views November 21, 2018 aetm 0

Put simply, we’re interested in designing for a human viewer, and not quantifying theoretical laboratory performance. The Standards define the contrast between the peak white and black levels under normal viewing conditions.

The test pattern is the 16-zone checkerboard with alternating black and white areas which was developed in the early days of electronic projection.

TIP: You don’t need an expensive test pattern generator for contrast – you can make it yourself in PowerPoint or any similar package

Don’t rely on the contrast figures quoted in projector/display manufacturer marketing materials. These numbers will be quite defensible (the Society for Information Display and the International Committee for Display Metrology published an extremely technical standard about display measurements) but describe the performance of the display under laboratory conditions. They have little bearing on a viewer’s experience.

For the four viewing categories, the required system contrast ratios are:

CategoryPISCRDVDISCR
Passive Viewing7:1TBA
Basic Decision Making15:1
Analytical Decision Making50:1
Full Motion Video80:1

 

‘Normal viewing conditions’ requires us to configure the house lights and blinds/drapes appropriately for safe movement and notetaking; and light any spotlights on the presenter. During the design process,

  • Negotiate your requirements with your Capital Works team so they can brief the design team adequately.
  • Engage with your lighting designer early and often – they may be able to influence the Architect’s luminaire selections and will definitely be able to predict the ambient light which will be incident on your displays.
  • Consider whether you need to conduct modelling to determine the impacts of daylight

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