Contrast Design of Visual Tone

Keeping an eye on the creation of visual contrasts will help you generating well-designed maps. If these most important visual contrasts are missing, the map user will lose interest in the map. A further consequence of missing contrasts is the difficulty in distinguishing between important and unimportant elements. The goal of contrasting elements is to emphasize perceptible differences and to give the eye the ability to discern them. Contrasts are achieved by modulating several visual variables: line, texture, value and colour. Below we suggest a few general principles of contrast:

Line Contrast
Lines are everywhere on a map: borders, neatlines, boundaries and symbols, for example, are very important map elements. Thereby, the need for well considered line contrasts emerge. There are 4 different possibilities for creating line contrasts that need to be taken into consideration when defining lines.

Have a look at the following specification:

Line Characters

A The most simple line character is shown – a black solid line
B The first variation is made in adding a stroke character to the basic appearance
C The second variation consists in adapting another line width to the stroked line
D The third possible variation is made by adding the colour or brightness components

For creation of well designed maps, line characters are not used in the same way as line widths. Indeed, a large line is visually dominant and brings more intellectual importance than a variable line character. Try to have different line characters and line widths on your map: a map with all lines of one width is boring and lacks potential in figural information.

Visual effect of varying line widths

These 2 examples will show you the visual effect of varying line widths on a map. In figure A , all the lines have the same widths, while three different line widths are used in figure B.

Do not overdo it with variations – they may confuse the map user. Stick to one line width within one information group! Have a look at the following rule from Richard D. Wright. It may be of help if you are confronted with choosing line widths to assure noticeable differences in maps.

Rule of Richard D.Wright

Rule of Richard D. Wright
(according to Wright (1967) cited in (Dent 1999))

Multiply the width of the current line by the coefficient 1.8. The outcome is the minimal width, which allows the differentiation for the second line.
If a third line is necessary, take the second line width and multiply it by 2.18 to have the width of the third line.
Finally, if a fourth line is still necessary, operate as you did for the third line, but with a coefficient of 2.52.

For example: If your first line width is 1

the second line weight will be 1.8 (1X1.8=1.8),
the third 3.9 (1.8X2.18) and
the fourth 9.8 (3.9X2.52 =9.8)

Texture Contrast
Texture is often chosen to represent quantitative or qualitative information, but without any contrast consideration. What is contrast of texture about? Contrast of texture involves areal patterns of small symbols. They are repeated in such way that the eye can perceive the individual elements and are chosen for different reasons:

Patterns can be used on a map solely to provide graphic contrast
Texture is sometimes applied in order to direct the reader’s attention to a particular part of the map.

Pattern Textures

Colour Contrast
The most applied technique in the designing process is to make use of colour contrasts. They are of major importance, as its impression has an immediate affect on the user. Colour contrasts and colour in general, as they are a major design element, are treated in detail within the Colour Design unit.

All mentioned principles of design contrasts could be used within one project layout but the result might be visually disharmonious or might appear without contrasts at all.
Designing with contrasts requires careful juggling with lines, textures, and colour-characteristics. It is a subtle element to use economically and with care. In the beginning, much may be generated by trial-and-error, but in most cases, you will see intuition to be explainable by designing rules. Then you will choose the right combination built up on your experience and knowledge.