Geography Reference
In-Depth Information
potential to change the way a color is perceived. [
] Not only are colors them-
selves unstable, ideas about colors are unstable as well” (Holtzschue
2011
, p. 11).
Not only physiology, also psychology and cultural background effect how people
see and interpret color. The subsequent paragraphs outline the most important
principles.
...
Color Contrast
Color contrast is a result of the perceived difference of at least two colors. The
World Wide Web Consortium
(W3C) defined straightforward recommendations on
color contrast in their “Web Content Accessibility Guidelines”. Comparable rules
are not available for maps because they do not just consist of background and text
that have to be balanced. It is necessary to consider the different kinds of contrast.
Classical contrasts are the ones between two colors: light and dark, warm and
cool or complementary colors (red/green, yellow/purple, blue/orange). Special
contrasts are quality and quantity contrast (Itten
1987
). The first occurs when colors
of different saturation or purity are combined. The latter describes the effect when
contrastive saturations are used for objects of different sizes. Itten (
1987
) suggests
to use colors only in harmonic proportions otherwise it results in an
effect of depth
and warm or saturated colors appear further in the front than cool or unsaturated
colors. Especially saturated yellow, orange and red have the characteristic to be
salient, therefore they should only be used for values that are meant to be
highlighted and in lesser amounts in contrast to blue and green. Figure
1a
illustrates,
how yellow and orange stand out in contrast to other colors in the map. Hence “the
intensity of color which should be used is dependent on the area that that color is to
occupy” (Ihaka
2003
).
The described contrasts together cause simultaneous-contrast that effects the
appearance of colors in dependence on adjacent and background colors. Light
colors surrounded by light colors look darker than surrounded by dark colors. An
object surrounded by an unsaturated or complementary color appears more satu-
rated than on saturated background (L¨bbe
2012
). This effect is hard to avoid and
predict because the spatial patterns in maps differ significantly.
Effects on Perceived Object Size
Schumann and M¨ ller (
2000
) describe that the perceived purity of a color is
dependent on the object size: A small colored area on black background is per-
ceived more saturated than a bigger area of the same color on black background. In
contrast, the color of an object has effects on the perceived object size too because
lighter colors stimulate retinal cells more due to higher light reflection (Schumann
and M¨ ller
2000
, p. 85). Consequently colors can facilitate misinterpretation if the
area size needs to be estimated for interpretation.
