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We will review chapter 12 (Color on Maps) from the Making Maps book. Additional information and examples can be gleaned from the material below.

• Making Maps Ch 12. Color on Maps
  • Cynthia Brewer Map Color Guidelines (below)

  • ColorBrewer

  • Making Maps Blog: Map Color Resources
    

Introduction

Color is fundamentally important to cartography and fundamentally confusing

• In the past: traditional printed maps: expensive and difficult to use color

• Given current computer technology, color is seldom NOT an option
  

  Bad Map. No Donut.

Mark Monmonier: Color as a cartographic quagmire: why?

"I do not advance that the face of our country would change if the maps which Philadelphia sends forth all over the Union were more decently colored, but certainly it would indicate that the Graces were more frequently at home on the banks of our lovely rivers, if the engravers were able to sell their maps less boisterously painted and not as they are now, each county of each state in flaming red, bright yellow, or a flagrant orange dye arrayed, like the cover produced by the united efforts of a quilting match. When I once complained of this barbarous offensive coloring of maps, the geographer assured me that he would not sell them unless bedaubed in this way; 'for, said he, the greatest number of the large maps are not sold for any purpose of utility, but to ornament the walls of barrooms. My agents write continually to me to color high.' This reason was given me by one of the first geographers of the United States, who has himself a perfectly correct idea of the tasteful coloring of maps."

--from Francis Lieber, "On Hipponomastics: A Letter to Pierce M. Butler," Southern Literary Messenger 3 (5) (May 1837): 297-300.

• color is confusing and there are no specific standards

  
  

• many different ways to specify colors

  
  

• color is often misused with new technologies

  
  

• there is a lot that you can do with black and white
  

  State College PA Night Map

Discussion of color and cartography:

1. An Introduction to Basic Color Terms and Perception

2. The Complexity of Color Use

3. Color and Cartographic Design

4. Color Hue and Color Value on Choropleth Maps

1. An Introduction to Basic Color Terms and Perception

1a. How Do We See Colors?

Color perception issues: the sensing and understanding of color: three elements

1. Characteristics of the light source

• colors will vary as the light source varies

• incandescent vs florescent, low light vs high light intensity

  
  

• design issue: under what kind of light source will your map be viewed?

2. Characteristics of the surface of the map

• colors will vary as the surface of the map varies

• glossy paper vs rough paper vs computer screen

  
  

• design issue: what kind of surface is the map presented on?

3. Characteristics of Human Color Perception

Humans are sensitive to a small band of electromagnetic energy which is called visible light

McKnight 2-23: Electromagnetic Energy Spectrum

Using color for cartographic design requires an understanding of how people perceive color

Dent Plate 7: Munsell Plate: the dimensions of color perception

Human color perception consists of...

1. hue: names for psychological experiences of particular electromagnetic wavelengths

• humans can perceive millions of different hues

• visual variables: hue suggest qualitative differences

2. value (lightness): perceived lightness and darkness

• easy to understand in a chromatic (color) or achromatic (greys) series

• humans can perceive thousands of variations in value or lightness

• visual variables: value suggests quantitative differences

3. saturation (chroma): amount of pure hue in a color relative to neutral grey

ex) radishes and tomatoes
visual variables: saturation suggests both qualitative and quantitative differences

1b. How Do We Create Colors?

Color production issues

We create colors in ways that are often different from the way we perceive colors

Dent Plate 12: Various Color Specification Systems

Color specification systems: schemes which organize and help produce different colors. There are numerous ways to organize and produce colors, all of which are used by cartographers and graphic designers.

Most color specification systems provide some kind of unique identifier for each different color in the system: they help specify unique colors for printing and for computers

Three categories of color specification systems you need to be familiar with:

A. Perceptual Color Systems: based on how humans see colors

Dent Plate 1: Munsell System

Munsell Color System: a three dimensional color space which is based on hue, value, and chroma/saturation; each color chip is differentiatable by the average viewer

Munsell Computer Palette: hue/value/saturation




ArcGIS Demo) Hue, Value, Chroma/Saturation in AV

B. Predefined Color Systems

Pantone Matching System: series of preselected colors which are available to commercial printers; you select a color and the printer obtains the correct ink mixtures

Pantone System

Use Pantone when you are going to have a map printed by a commercial printer. Also provides a diverse palette of colors.

ArcGIS Demo) Specific Color Palettes in AV

Different for color production in printing vs on computer screens

C1. Process color systems for printing (commercial printers)

Process Color Chart: 20% cyan and varying % of yellow and magenta






Dent Plate 11: Process Print Closeup

You can get a broad range of colors (hue, value, chroma) based on varying combinations of cyan, magenta, and yellow

ex) 40% yellow, 10% cyan, 5% magenta = unique color

Color Primaries

Color Primaries: additive and subtractive

Cyan, magenta, and yellow are called the subtractive primaries

when all three are combined, they subtract (absorb) all light resulting in black

Subtractive Primaries are the most common system used in printing

printed colors reflect light and you see color

Problem: if you want black you can get it by combining 100% of cyan, magenta, and yellow, but resulting color is a very dark brownish color

• therefore black is added as a fourth 'color' to overcome this problem

• CMY(K): cyan, magenta, yellow, black

  
  

  PHOTOSHOP DEMO) Subtractive Primaries

C2. Process color systems for computer screens

Color Primaries: additive and subtractive

RGB: red, green, blue are called the additive primaries

when all three are combined, they add (reflect) all light resulting in white

You can get a broad range of colors (hue, value, chroma) based on varying combinations of red, green, and blue

Robinson: Close up of computer monitor




PHOTOSHOP DEMO) Additive Primaries

Additive Primaries the most common system used in creating color on computer screens (and computer printers)

displayed colors project light and you see color

Color specification in HTML: Hexidecimal Color Specification System

• A means of describing RGB in hexadecimal digits:

• two digits for red, two digits for green, and two digits for blue

• 00 is black (absence of color) and FF is maximum intensity.

• range of values from light green to dark

• 00FF00: no R, max. G, no B
  ex) 00FF00 >> 00EE00 >> 00DD00 >> 00CC00 >> 00BB00 >> 00AA00 >> 009900 ...

Many excellent Color HTML sites on the WWW:

Yahoo Color WWW Sites

2a. Color Interacts with its Environment

Simultaneous contrast: the appearance of any color in a display depends on the colors that surround it

Robinson 21.1: Simultaneous Contrast

This is an artifact of the way our brain interprets color

Carefully pre-selected colors (selected independently of each other) will often look different when combined on a map

Little we can do about it except to carefully evaluate the way colors interact together on a map

Successive contrast: colors are modified based on the order in which they are seen; related to simultaneous contrast

ex) look at orange symbol, then black symbol, then orange

Successive Contrast

Visual acuity: monochromatic backgrounds (one hue) make it easier to pick out colors than mixtures (such as brown)

Visual Acuity

Advance and retreat: perceptual phenomena whereby reds seem to advances (stand out more) and greens and blues seem to retreat (fall back more) in the visual plane

Hypsometric Effect






Hypsometric Effect: Relief Map


Hypsometric Effect: convention to use this effect to enhance relief on maps
problem with emotive effects (dry/wet)

Why does advance/retreat happen? Our eye physically adjusts itself a bit when perceiving longer wavelength reds and this seems to produce this effect; very subtile

• high values seem to advance and low values seem to retreat

• high saturations seem to advance and low saturations seem to retreat

Individuality of Hues

• some hues look "individualistic" and others look like mixtures
  

  Individuality of Hues

  
  

  ex) blue + yellow = green but green does not look like a mix

  ex) red + yellow = orange and orange does look like a mix

Implications:

• phenomena which is distinctive should use individualistic hues

• phenomena which is mixed should use mixture hues

Color location, size, and shape: colors will seem to vary as their location, size, and shape varies

Implications of all of these issues: color cannot be selected independent of its context

2b. Changing External Conditions Affect Perception

The appearance of any color in a display varies as the lighting conditions of the room the display is in change

• incandescent vs florescent lighting

• dim vs bright lighting

• turn room light on and off and notice colors change on wall maps

Color varies as the settings of one computer monitor vary

Implications:

• for printed maps: try and take into account the viewing conditions if known

• most important if dim lighting conditions are expected

• for computer displays look at your display on different monitors, and make sure you look at it on the one your map will be used on

2c. Physiological Differences among Individuals

The appearance of any color in a display varies based on who is viewing it

Young children (less than 5 yrs old) seem to understand only a limited set of hues, and have difficulty arranging different color values in any kind of order

• preference for warm hues such as reds and greens

• switch to preference for cold hues (blues) later in life

• trouble with highly saturated hues (which is common on kids maps)

• trouble with highly unsaturated hues

Older people are less sensitive to color and need brighter (saturated) colors

• older people lose the ability to perceive blue

Color blindness in 3% of females and 8% of males (red and green look same)

• using colors that are colorblind safe

...finally: color use is complex because...

Tufte: Seasons

2d. Color has Symbolic and Emotional Connotations

The meaning we get from different colors varies

• culturally determined in many instances

Our culture has conventional meanings for different colors

• blue: water, cool, positive numerical values, serenity, depression, melancholy, truth, purity, formality, depth, restraint, loneliness

• green: vegetation, lowlands, forests, youth, spring, nature, envy, greed, jealousy, cheap, ignorance, peace

• red: warm, important items (roads, cities...), action, life, blood, fire, heat, passion, danger, power, loyalty, bravery, anger, excitement, warning

• yellow/tan: dryness, lack of vegetation, intermediate elev., "hot", cheerful, dishonest, youth, light, hate, cowardice, joy, optimism, spring, strong, warning

• orange: harvest, fall, abundance, fire, attention, action, warning

• brown: landforms (mountains, hills...), contours, cozy, dull, reassuring, depressing

• purple: dignity, royalty, sorrow, despair, richness, elegant

• white: purity, clean, faith, illness

• black: mystery, strength, heaviness

• grays: quiet, reserved, sophisticated, controlled

Implications: use these conventions to match phenomena with color

• examples

3. Color Hue and Color Value and Choropleth Maps

"Appropriate use of color for data display allows interrelationships and patterns within data to be easily visualized. the careless use of color will obscure these patterns."

Poor and Good use of Color Value on Choropleth Map

Brewer's guidelines are derived from two sources

• long history of graphic design experience: the 'art' of cartography

• but also perceptual/cognitive studies: the 'science' of cartography

In essence: we want color use to be as intuitive as possible

• user does not have to think about the symbolization

• but can focus on the patterns on the map

Brewer's Color Guidelines

WWW) Brewer Color Schemes On Line

WWW) Colorbrewer

General rule of thumb: hue for qualitative differences, value (lightness) for quant/ordered

1. One Variable Color Schemes

• for single-variable choropleth maps: most common

1a. Qualitative Schemes: qualitative difference in data

• represent with differences in hue, holding value constant
  

  Brewer: Qualitative Color Scheme (Hue)

1b. Binary Schemes: qualitative difference in data

• represent with differences in value, holding hue constant

• unique case: using value to represent qualitative difference
  

  Brewer: Binary Color Scheme

1c. Sequential Schemes: some order or sequence in the data (quantitative)

• represent with differences in value, holding hue constant
  

  Brewer: Sequential Color Scheme: Monochrome

  
  

  

  Brewer: Sequential Color Scheme: Chromatic (single hue)

  
  

  

  Brewer: Sequential Color Scheme: Chromatic (multiple hue)

1d. Diverging Schemes: importance focused on a mid point and variations out from that midpoint

Brewer: Diverging Color Scheme: Chromatic (green/yellow)






Brewer: Sequential Color Scheme: Chromatic (red/blue)

• For representing two and three data variables at the same time

• Less common, harder to interpret, but more sophisticated

• For more sophisticated users

• Can create such color schemes in ArcGIS manually (custom colors)
  

  Brewer: Two Variable Color Scheme: qualitative/binary

  
  

  

  Brewer: Two Variable Color Scheme: qualitative/sequential

  
  

  

  Brewer: Two Variable Color Scheme: sequential/sequential

  
  

  

  Brewer: Two Variable Color Scheme: sequential/sequential

  
  

  

  Brewer: Two Variable Color Scheme: diverging/sequential

  
  

  

  Brewer: Two Variable Color Scheme: diverging/diverging

  
  

  

  Brewer: Three Variable Color Scheme: diverging/diverging/diverging

Summary

An overview of the many issues surrounding the use of color to represent information

1. An Introduction to Basic Color Terms and Perception

How Do We See Colors?

• light source, surface, and perceptual issues

How Do We Create Colors?

• color specification systems

2. The Complexity of Color Use

• Color Interacts with its Environment: simultaneous and successive contrast, visual acuity, advance and retreat, individuality of hues, color location, size, and shape

• Changing External Conditions Affect Perception: lighting conditions and computer monitors

• Physiological Differences among Individuals: children, elderly, colorblind

• Color has symbolic, emotional, and affective connotations

3. Color Hue and Color Value and Cartographic Design

Brewer's scheme whereby the perceptual dimensions of color correspond to logical organization of the mapped data

Color misused more than other visual variables

Remember: variations and changes in color should mean something

• avoid gratuitous use of color

• attempt to correlate variations in the data with logical variations in color

Avoid creating your own cartographic quagmire!

E-mail: jbkrygier@owu.edu

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