licht.wissen No. 01 "Lighting with Artificial Light"

licht.wissen 01
Lighting with Artificial Light
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warm white (ww) neutral white (nw) daylight white (dw)
2,700 – 3,300 Kelvin 3,300 – 5,300 Kelvin über 5,300 Kelvin
cosy light
functional light
Light colour – From warm to cool
We experience our environment not only through light and shadow, but also through colour. The light colour
of a lamp also determines the spatial impression and is an important criterion in the planning of biologically
effective lighting.
[52] The light colour of the lamp used determines
the impression of the room: from
homely/warm white through to functional
daylight white.
The light of each light source has its own
so-called light (or luminous) colour. It is described
by its colour temperature, measured
in Kelvins (K). The higher the temperature
value, the cooler white the light colour.
The Kelvin temperature scale starts at absolute
zero (0 Kelvin = -273.15° C).
Determining colour temperature
Heating up the tungsten filament of an incandescent
light bulb (for example) lights it
up red initially, then yellow and finally white.
The physicist Max Planck developed a
mathematical formula for this kind of “temperature”
radiation. It can also be used to
describe light colours above the melting
temperature of tungsten.
In order to determine the colour temperature,
the colour impression of a lamp is
compared in the human eye to that of a
standardized “black body”, the light colour
of which is determined by its temperature.
When such a black body is heated, it
passes through graduations of colour from
red, orange, yellow and white through to
light blue. To represent clearly the perceptible
colour space, the international lighting
commission CIE developed a two-dimensional
chromaticity diagram. This coordinate
system contains all spectral colours on
a horseshoe-shaped curve: the black-body
curve of all colour temperatures of white
light. In the centre is the white point W
(= no colour). Here, all colours are present
to an equal amount (x = 0.33 / y = 0.33).
The colour of a light source is indicated on
or right next to its CIE spectrum locus in
the colour table depending on its colour
temperature. This temperature is identified
by the closest colour temperature (T cp ).
This is the temperature that heated platinum
requires to take on the same colour
as the light source. Therefore low colour
temperatures of up to approximately
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