Color and Design

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Color and Design

• Francis Li
• With contributions from Prof. Marti Hearst
• CS160 Discussion
• November 16, 2000

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Outline

• Pre-attentive Processing
• Using Color
• Some Principles of Color
• Color as Quantity
• Summary

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Pre-attentive Processing

• Some visual properties can be processed without
  need for focusing attention
• Color is one of them!
• This is important for design of visualizations
• what can be perceived immediately
• what properties are good discriminators
• what can mislead viewers

All Preattentive Processing figures from Healey
97http//www.csc.ncsu.edu/faculty/healey/PP/PP.ht
ml
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Example Color Selection
Viewer can rapidly and accurately
determine whether the target (red circle) is
present or absent. Difference detected in color.
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Example Shape Selection
Viewer can rapidly and accurately
determine whether the target (red circle) is
present or absent. Difference detected in form
(curvature)
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Pre-attentive Processing

• lt 200 - 250ms qualifies as pre-attentive
• eye movements take at least 200ms
• yet certain processing can be done very quickly,
  implying low-level processing in parallel
• If a decision takes a fixed amount of time
  regardless of the number of distractors, it is
  considered to be pre-attentive.

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Example Conjunction
Viewer cannot rapidly and accurately
determine whether the target (red circle) is
present or absent when target has two or more
features, each of which are present in the
distractors. Viewer must search sequentially.
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Pre-attentive Properties

• length Triesman Gormican 1988
• width Julesz 1985
• size Triesman Gelade 1980
• curvature Triesman Gormican 1988
• number Julesz 1985 Trick Pylyshyn 1994
• closure Enns 1986 Triesman
  Souther 1985
• colour (hue) Nagy Sanchez 1990,
  1992 D'Zmura 1991 Kawai et al.
  1995 Bauer et al. 1996
• And many more on Healys webpage

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Using Color

• Label
• Color as noun
• Measure
• Color as quantity
• Represent or Imitate Reality
• Color as representation
• Decorate
• Color as beauty

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Cartographic Example
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Some Principles of Color

• Eduard Imhof, Cartographic Relief Presentation
• Design practices for Swiss maps
• First Rule
• Color spots against a light gray or muted field
  highlight and italicize data
• Second Rule
• Large patches of light, bright colors next to
  each other is bad

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Good or bad?
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Good or bad?
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Color as Quantity

• Distinguishing colors
• Trained colorist 1,000,000 colors
• Most people 20,000 colors
• Visual memory, not perception, becomes the
  problem
• Practical limits
• 20-30 colors max

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Cartographic Example
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Limitations

• Perceived color shifts
• Can be misleading!

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Same or Different?
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Same or Different?
The small squares are the same color.
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Limitations (cont)

• Contour lines can help alleviate (as in maps)

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Summary

• Color is a Visual Pre-attentive Property
• Color can be used to
• Label
• Measure
• Represent or Imitate Reality
• Decorate or Enliven
• But watch out for quirks in perception