Colour rendering & Light colour of lamps

Sunlight contains all of the colours visible to human beings. With lamps, there are various colour rendering properties. To be able to name these, the value CRI measures colour rendering. The higher this is, the better the colour rendering. An optimum value here is CRI 100, for here all colours are rendered naturally.

Human beings experience their environment not only as light and dark, light and shade, but also through colours. The colour designation of lamps consists of three figures. The first figure identifies the colour rendering, the Raarea, the second and third figures the colour temperature in Kelvin.

Colour rendering

1. figure Raarea

9 = 90 - 100

8 = 80 - 89

7 = 70 - 79

6 = 60 - 69

5 = 50 - 59

4 = 40 - 49

Light colour

2nd + 3rd figure Colour temperature

27 = 2700 K

30 = 3000 K

40 = 4000 K

50 = 5000 K

60 = 6000 K

65 = 6500 K

People’s moods can be influenced by warm or cold colours. The colour impression is determined by the interaction between colour and the viewed objects (spectral reflectance).

Warm light colours (up to approx. 2900 K) have a calming effect and ensure a comfortable living situation.

Cool light colours, on the other hand, have a higher blue content (over 3300 K) and have an invigorating effect. These are used in places where concentration or an objective mood is to be encouraged.

Colour temperatures in Kelvin:

warm white < 3300 K

neutral white 3300 - 5300 K

daylight white > 5300 K

Since the light from lamps with the same light colour may have a completely different spectral composition, it is not possible to draw conclusions from the light colour of a lamp about the quality of its colour rendering.

The colour triangle defined by the International Commission on Illumination CIE shows how light sources and body colours are to be classified.

Achromatic, that is, white when brightness is high and grey or black in the dark, is at x = y = 0.333. The other chromatic colours are around this achromatic point. All spectral colours of sunlight are on the straight line between achromatic and the limiting curve. Colours with the same hue, which gains in saturation in the direction of the limiting curve, can also be found there. The colour triangle thus contains all real colours. The Planckian locus describes the colours of the “black body” at the specified temperature values in Kelvin.