Is color objective or a perception

Colors and color perception


The phenomenon of color


Colors are something very common, something that we are only too happy to take for granted and immutable. Viewed objectively, however, colors are a purely psychological phenomenon that is transformed into something concrete by the human senses. From a physical point of view, color is only light with different wavelengths of approx. 380nm - 780nm.


Physiological basics


It is only the sensory cells (photoreceptors) present on the retina and the further processing of their signals in the brain that create the colorful world we know. Only a part of these receptors is responsible for color perception, the so-called suppositories. In contrast to this are the very light-sensitive rods that enable us to see in darkness and twilight, but all have the same spectral absorption, which is why they cannot differentiate between wavelengths and intensity levels, i.e. they are color-blind. However, since these are completely saturated in daylight and are therefore unable to absorb information, the suppositories are now active. These are divided into three different types, characterized by their spectral sensitivities. The red cones (L cones), which are sensitive in the long-wave range, have the greatest sensitivity, misleadingly, in the wavelength range that we perceive as yellow. The green cones (M cones) are most sensitive in the medium wavelength range. The blue cones (S cones) are responsible for the short-wave range. However, these have their maximum not with blue but with a rather violet color.
In the center of the retina there are only red and green cones, the blue cones only appear in the periphery and there only in a lower density. In general, the proportion of blue cones is only around 5-10%, green cones are around 30% and the proportion of red cones makes up around 65%. The fact that the density of the cones correlates with the visual acuity means that patterns that only excite the blue cones are only allowed to have a very low resolution.
Each combination of stimuli from the three types of cones caused by the radiation hitting the retina produces a specific color impression. However, identical color impressions can also be achieved through different spectral combinations of the light. This effect is called metameric color equality and is often used in technology. For example, a pixel of an LCD monitor can be displayed in almost any perceptible color by combining three TFTs (Thin Film Transistor), each of which shines in different colors - red, green and blue.
In the diencephalon, three new signals are formed from the three individual signals for red, green and blue. A sum signal of red and green (R + G), a difference signal of red and green (R-G) and a difference signal of yellow (corresponds to the sum signal of red and green) and blue ((R + G) -B). R-G and (R + G) -B are responsible for differentiating the respective color tones (red / green and blue / yellow), whereas R + G primarily takes on the task of perceiving brightness.
These human visual apparatus can distinguish 128 different color tones, 130 different color saturations and 16 (in the blue area) or 26 (in the yellow area) different brightness values. As a result, the number of perceptible colors is limited to 380,000, so, for example, far more colors can be displayed on a monitor with a color depth of 24 bits about 15 different colors), which can be displayed at the same time.


Color theory


The current theory of colors comes from Harald Küppers and was developed until the mid-1970s. Through them, some aspects of older color theories, such as Johannes Itten's, have proven to be wrong when applied in practice. Eight basic colors form the basis for Küpper's teaching. In addition to the three original colors: red, blue and green, he counts three combinations (cyan, magenta, yellow) - of two of them in equal parts and in full intensity - among the six basic colors. Together with black and white - the achromatic basic colors - you get the full eight.
If the basic colors are arranged in a hexagon (the combinations are between the original colors), any number of intermediate colors can be achieved by mixing adjacent colors. This hexagon can be divided into 2 halves, one of which contains warm and the other cold shades. The warm colors range from green to yellow, red to magenta. The cold shades range from magenta to blue, cyan and green. Green and magenta are at the interface between warm and cold and are considered neutral. The peculiarities of human color perception and their consequences for design will now be discussed in more detail below.


Effect of individual colors

If you look at the basic colors in isolation, they evoke certain emotions and associations in humans. For example, one associates the color red with energy, love, passion, fire and warmth, but also anger, anger, sin and danger. Blue creates trust and ensures calm, but can also convey negligence and melancholy. These two colors are also a good example of a warm (red) and a cold (blue) color. These aspects, together with other factors that are shown in the next paragraph, have a strong influence on the perception of publications, for example, and should therefore be carefully considered.


Color design


In order to create a positive overall picture, you have to strive for a harmonious color image. This can be achieved, for example, by combining adjacent color tones, using lightened color tones with their full color tones or by combining colors from the warm or analogous to the cold color palette. To emphasize, be it to clarify differences, or to draw attention, contrasts are particularly suitable. The complementary, light-dark and simultaneous contrasts deserve special mention here. The complementary contrast is achieved by using two colors that are opposite each other in the color hexagon and complement each other to achromatic (e.g. blue and yellow). In the light-dark contrast, the full colors are used with their lightened hues. The simultaneous contrast has a special position here, namely it says nothing specifically about the design, but rather about how colors work in context. One and the same color appears lighter against a dark background and darker against a light background, but the hue also changes with a changing background. Achromatic backgrounds make bright colors shine more, colors appear cooler against warm colors and vice versa. The reason for the simultaneous contrast is based on the fact that the human visual apparatus is not intended to reproduce colors as precisely as possible, but to make the differences clear.
Finally, color tones should now be mentioned. These are color combinations that have a high-contrast effect, but are nevertheless harmonious, so they are well suited to differentiating between content that is not in contrast to one another. Color sounds have the property of being the same distance from each other in the color hexagon, so they can be put together by placing equilateral surfaces over the color hexagon (e.g. triangles or squares), the end points of which then point to one of the color tones. A color triad would therefore be the triangle formed by cyan, magenta and yellow.
A lot of mistakes can be made in the color design of publications, so it is essential to be clear about the color effects. Not only can a negative impression be avoided, but a very positive impression can also be created.


literature


http://www.ipsi.fraunhofer.de/Kueppersfarben/de/drucken.html
http://www.ipsi.fraunhofer.de/~crueger/ Farbe/farb-ffekt.html
http://www.kdow.de/text/farbffekt/farbw.htm
http://www.psychologie.uni-heidelberg.de/ae/allg/lehre/wct/w/w5_color/
http://www.allpsych.uni-giessen.de/karl/teach/ Farbe.html
http://www.weblexikon.de/Farbwahrendung.html
http://de.wikipedia.org/wiki/Farbwahrsehen

Henning, Peter A .: Pocket Book Multimedia, Leipzig, 2003;




© Matthias Marm 12.12.2004