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Ambient light à l'Ethiopienne: newspaper plastered walls reflect the light beams and create a bright atmosphere.

What is good light?

Artificial light has developed steadily since the first lamps burning animal fat circa 40,000 years ago. Nonetheless, there is still no simple patent recipe for good light even today. The right mixture of daylight and artificial light, direct and indirect lighting, must, in any case, be adjusted to each context and the needs of the user, and is additionally subject to different culturally shaped perceptions.

It defines our lives in a way that almost no other element does. And yet we often first notice it when it is missing: light is one of the most important elixirs, and not only for people, but also flora and fauna. Light determines our sense of time, separates day from night. Light lends objects shape and form and controls our sense of color. The quality of light also influences our mood. On dreary, cloudy winter days a lot of people in northern countries suffer from a phenomenon known as seasonal depression and are often treated by means of light therapy.
In today's western world illuminated by artificial light, one can barely imagine the sensation caused by the stone lamps run on animal fat and the accompanying change in daily routine 40,000 years ago. Further essential innovations—the Romans' lamps burning with beeswax, oil lamps, the first gas lanterns at the beginning of the nineteenth century, and especially Edison's light bulbs in1879—followed in increasingly shorter intervals. Along with advancing development, artificial light became not only lighter, but also safer, more emission-free, and quieter. Edison's invention brought an end to the latent danger of fire and steadily present odor of gas in broad parts of the world. The crackling of a fire became a quietly gasping flame and in the end an almost silent click of a hand on a light switch. The LCD lamps used since the 1920s and the LED lamps used in even greater dimensions since the 1960s, require, in addition, less energy and are more durable: the latest generation of LED lamps lasts up to twenty-five years and uses roughly ten times less electricity than light bulbs.
Their light quality is, however, disputed, as shown, for example, by the case of the Christmas lights on Zurich's Bahnhofstrasse (2005–2009). The rod-shaped LED lights, which conjured up a light play on the elegant street by means of software programming, were not very well received by the population despite their frugal and futuristic technology. Too garish, not warm enough, not Christmasy enough were the scathing criticisms. Developers reacted to such criticism: meanwhile, LEDs with a warmer light are also on the market.
The American light pioneer, Richard Kelly (1910–1977), who among other things, lit up Mies van der Rohe's Seagram Building, differentiated three basic functions of artificial light: ambient light illuminates the surroundings and a space and enables the perception of people and objects; light to follow (focal glow) attempts to arrange the hierarchy of perception in a space by means of the distribution of light within a wealth of information; and light to look at (play of brilliance), a light source that itself becomes information, for example, the flame of a candle or the sparkling of a chandelier to mediate a particular mood. Previously a stage illuminator, Kelly approached a space to be illuminated as he would a stage in order to evoke a certain mood and set accents by means of the staging of light. Inside, light does much more than make perception possible. It is meant to create an atmosphere, make spaces seem larger or smaller, border or link areas, and highlight details.
Light planners can calculate the physical qualities of a lighting situation quite easily nowadays. Decisive for a consistent lighting situation are, in the end, the extremely complex process of vision and subjective perception of each individual. For that reason, light planning must take into consideration not only technical aspects, but also human awareness and knowledge from the psychology of perception. Another important principle is the phenomenon of perceptual constancy, which says that the recognition of brightness, color, material qualities, form, and spatial dimensions is not influenced by changing environmental factors, such as differences in lighting, changing light colors, or distance. A black object in direct sunlight has a significantly higher light density than a white object in the shade. Nonetheless, the white object is recognized as white and the black as black. Due to the constancy of degree of reflection, perception is not dependent on light density so that the true shapes of the objects are recognized. People's perception of color is also amazingly constant under changing lighting situations. As long as no comparison is possible (for example, via light sources with better color reproduction), astonishingly, people perceive colors as authentic.
Also important is the fact that light is valued differently in different cultures. In southern countries, neutral white to daylight white light colors are preferred, which suggest "coolness" on hot days. In northern countries, the reverse trend can be found: warm, also often indirect light that lends the space a comfy atmosphere. While Chinese culture prefers what appears for Western perception to be a kitschy artificial light in as many different colors as possible, Japan, which can refer back to a centuries-old and deeply traditional lighting culture, uses artificial lighting rather sparingly. Shadowing, thus has a particularly important status in Japanese culture.
All of this thereby makes obvious that the question of good light cannot be answered clearly, but instead, produces different answers depending on the context and cultural background. 

Source:  sun-connect 4 | November 2010 (p. 2-3)