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Colour in map design by Alastair Pearson

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Subtractive colour mixture. mixing pigments. absorb and reflect parts of spectrum. subtractive colour primaries (CYAN, MAGENTA, YELLOW) mix primaries to produce ... – PowerPoint PPT presentation

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Title: Colour in map design by Alastair Pearson


1
Colour in map designbyAlastair Pearson
Geographical Data Presentation
2
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3
Reasons for concern
  • Colour graphics more affordable
  • Unlimited freedom to select, mix and use colour
  • Poor guidelines with software
  • Unhelpful colour descriptions - wheels, triads,
    RGB settings)
  • Poor default colours

4
Functions of colour in map design
  • Robinson (1967)
  • 1. Simplifying and clarifying agent.
  • Development of figure-ground organization
  • 2. Affects the perceptibility of the map.
  • Legibility, visual acuity, and clarity.
  • 3. Elicits subjective reactions to the map.
  • People respond to colours - connotative and
    subjective.

5
Functions of colour in advertising
  • Attract buyer's attention
  • Stimulate interest
  • Identify products
  • Relate successive advertising
  • Provide emphasis
  • Illustrate, interpret and prove
  • Lead reader's attention
  • Embody prestige
  • Functions of design for mapping are similar.

6
What is colour?
  • a complex eye-brain response to
    electromagnetic radiation in the visible portion
    of the electromagnetic spectrum, commonly called
    'light'

7
  • human perceives light 400nm to 700nm (1nm
    1/1000 of a micron) in wavelength
  • 6 "spectral" colours - violet through red
  • colour of objects functions of-
  • illumination source
  • object's reflectance ability
  • sensitivity of cones in our eyes

8
Spectral Colour circle
  • usually visible colours only
  • mix opposite colours GREY (complementary)

9
Additive colour mixture
  • mixing light
  • additive colour primaries (RED, GREEN, BLUE)
  • mix primaries to produce almost any colour
  • vary energy level

10
Subtractive colour mixture
  • mixing pigments
  • absorb and reflect parts of spectrum
  • subtractive colour primaries (CYAN, MAGENTA,
    YELLOW)
  • mix primaries to produce most colours
  • vary quantity

11
Colour specification systems
  • Early systems - subjective/psychological
  • Later systems - objective/physical spectrometry
  • Increasing use
  • cartographers need to specify exact colour
    specifications
  • researchers in cartography need to refer to the
    same colour
  • systems enable us to conceptualise
    interrelationships of hue, brightness and
    saturation

12
2 worthy of note -
  • (i) C.I.E. Colour Specification
  • (ii) Munsell Colour Solid - N.America

13
(i) C.I.E. COLOUR SPECIFICATION (Commission
International de l'Eclairage)
  • physical colour specification system
  • describes physical properties of colour
  • specified in numerical terms
  • measures mix 3 additive primaries in varying
    intensities (tristimulus values)

14
Summary-
  • objective system
  • specifies each colour precisely
  • based on additive light
  • not based on human visual perception
  • not that relevant to cartographers

15
(ii) Munsell Colour Solid (Albert H. Munsell
1858-1918)
  • 3D representation of colours
  • hue, value, saturation are axes
  • based on human visual perception
  • equal visual steps

16
Description
  • Hue
  • 100 hues in circle
  • 10 major hues (5 principle, 5 intermediate)
  • ordered according to spectrum
  • Value
  • vertical axis
  • 0-10
  • 0 BLACK
  • 10 WHITE

17
  • Chroma
  • horizontal axis
  • 0-14 or 16
  • 0 grey
  • 14 or 16 pure hue (full saturation)
  • EXAMPLE 5.0 YR 6 10

18
Summary-
  • a) subjectively/psychologically based
  • b) human colour perception
  • c) equal steps in appearance not physical reality
  • d) referred to by cartographers - thematic
    mapping - equal visual steps

19
Printing colour specifications
  • colour specification systems difficult to use in
    production
  • cartographer uses colour matching systems
  • cartographer specifies inks

20
Pantone Matching System
  • 8 basic colours black and white
  • over 500 colours
  • each colour coded
  • over 500 printing ink hues are possible

21
3 and 4 colour process
  • feasible to print map using as many inks as
    colours
  • cartographers use screens and overprinting to
    create value, chroma and often hue variation
  • printing often uses 3 or 4 colour process
  • CYAN, MAGENTA, YELLOW BLACK
  • BLACK often added - 4 colour process
  • screens regulate process colour
  • colour charts provide guide

22
Colour on video displays
  • Combines additive primaries (red,green,blue)
  • RGB Colour System- RED,GREEN,BLUE
  • gun for each colour fires electron beam
  • phosphor dot for each colour
  • 3 dots - 8 colours possible
  • vary with 256 intensities 16.7 million colours
  • 256 colours normal limit

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Qualitative conventions
  • Robinson (1967) colour conventions and
    associations
  • Blue for water
  • Red with warm, blue with cool
  • Yellow and tans for dry and little vegetation
  • Brown for land surfaces and contours
  • Green for lush and thick vegetation

25
Quantitative conventions
  • Cuff (1972) identifies four colour plans
  • 1. Grey and simple hue vary colour brightness
    only.
  • 2. Part-spectral plan colours adjacent on colour
    wheel show variations in amount
    (blue-green-yellow / red-orange-yellow)
  • 3. Full-spectral plan separate hue used to
    represent amounts (red, orange, yellow, green and
    blue for hypsometric tints)
  • 4. Double ended plan to illustrate bi-variate
    data or positive and negative data values (Dark
    red to light red then light blue to dark blue)

26
Possible solutions to misuse of colour (Green,
1993)
  • More input of cartographic expertise
  • More education and training in cartography to
    raise awareness and knowledge
  • More online tutorial and expert advice available
  • More software packages with emphasis on
    cartographic tools and applications
  • More research into map design in an electronic
    medium
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