8.3 Light and quality of life. Osram HQI-E 150 W/NDL CL
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8.2 Colour rendering
Colour is a sensory impression conveyed by the eye.
The evaluation of a colour stimulus by the eye causes a uniform effect (colour stimulus specification). This can be described by colourimetric numbers (e.g. x, y and z in the CIE 1931 or CIE 1976 colour space or
L, a and b in the CIE 1976 (L*a*b*) space or W, U and
V in the CIE 1964 colour space (W*, U*, V*)). But the perceived colour (the subjective impression) depends on the general conditions (colour mood, surrounding surfaces, luminance).
One way of showing the colour impression is the standard chart as per DIN 5033 – basic stimulus.
The primary colours, i.e. saturated monochromatic colours, run around the periphery of the colour triangle.
An ideal black body (or Planck radiator) radiates an electromagnetic spectrum depending on its temperature. The colour thus depending on temperature is depicted in the Planck curve, this is the so-called
“colour temperature”.
Colours on the Planck curve are marked with the corresponding colour temperature; chromaticity coordinates deviating only slightly from the Planck curve
(within the range of the Judd straight lines, corresponding to a distance of approx. 5.4 threshold value units) are marked with the correlated colour temperature.
Fig. 50: Standard colour chart as per DIN 5033
48
CRI: 50
R
4
: 46
R
5
: 43
R
6
: 36
R
7
: 66
R
8
: 44
Reference color temperature 4000K
HQL-Standard
R
1
: 46
R
2
: 61
R
3
: 54
HCI - NDL
R
1
: 99
R
2
: 97
R
3
: 88
R
4
: 96
R
5
: 97
R
6
: 95
R
7
: 96
R
8
: 93
CRI: 95
Fig. 51: Defining the colour rendering indices in comparison for two light sources
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