Philips Indoor Luminaires Indoor Furnishings User Manual


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Specication data lamps
Philips indoor luminairesTechnical data12.10
Color characteristics of lamps
Lamps do not all emit light of the same color. There is, for example, a
striking difference between the pronounced amber light from standard
sodium lamps and the white light from most other lamps. Even then,
one white light is not the same as another. To select the right light
source for the color characteristics required, two separate parameters
have to be considered, i.e. the color temperature of the emitted light
and its color rendering.
Color temperature
Giventhatthecolorofthelighthasanimportantinuenceonthe
color impression of the area, the color temperature of the light source
plays an essential role. To enable an objective comparison of the color
impressions from various sources, subjective terms such as the popular
words ‘cool’ and ‘warm’ are inadequate. A precise scale is required and
given by the term ‘correlated color temperature’; the color gradation
of the light is compared with the light emitted by an intensely heated
iron bar of which the temperature is known. In this way, the light color
canbespeciedbyavalueinkelvin(K).Alowcolortemperature
represents warm, yellow, orange or red light and a high color
temperature cool, blue or violet light.
Fourcategories,asapracticalguideline,are:
2500 - 2800 K warm/cosy
Thecolorfromincandescentlamps,(compact)uorescentlampsin
the colors 827 and 927 and the SDW-T White SON lamp. Generally
used for intimate and cosy environments where the emphasis is on a
peaceful relaxing ambience.
2800 - 3000 K warm/neutral
The color from halogen lamps, color 830 and 930 (compact)
uorescentlampsandMASTERColour830lamps.Usedinplaces
where people are active, requiring a welcoming comfortable ambience.
3000 - 5000 K neutral/cool
Thelightcolorfrom840and940uorescentlampsaswellas
MASTERColour942andMHNmetalhalidelamps.Usuallyappliedin
commercialareasandofceswherealookofcoolefciencyisdesired.
5000 K and above daylight and cool daylight
Thelightcolorthatbestmatchesnaturaldaylight,suchasuorescent
colors 850, 865, 950 and 965 and the new ActiViva colors 451 and 452.
Color rendering
The perception of surface colors, the color rendering of the light,
depends on the color content of the incident light. The light emitted
by a light source is composed of a mixture of colors, all in different
intensities. A change in the color mixture and intensity yields a
different color rendering.
Cooldaylightandincandescentlampshavefullynaturalcolor
rendering properties. The same is true for halogen lamps. The reason
for this is the continuous spectrum of the sources, which is typical for
lamentlamps.
Most gas discharge sources, however, have an interrupted or line
spectrum.Thishasaninuenceonthequalityoftheircolorrendering
properties,whichvaryfromverypoor,withSOXlow-pressuresodium
gas discharge lamps, to excellent, with the color 90 De Luxe series
uorescentandMASTERColour942lamps.
When selecting a particular lamp type, a clear understanding of the
color rendering properties is essential. A fair indication is given by the
colorrenderingindex(CRI),whichisastandardizedscalewith
100asthemaximumvalue.Colorsarebestshownunderalight
source with the highest color rendering index. Incidentally, it is
onlyworthwhiletocompareCRIvaluesoflampsofsimilarcolor
temperature.
In practice, three color rendering categories are
normally found.
CRIbetweenRa90and100.
Excellent color rendering properties.
Applications are mainly those where correct color appraisal is a
critical task.
CRIbetweenRa80and90.
Good color rendering properties.
Applications in areas where critical color appraisal is not the primary
consideration but where good rendition of colors is essential.
CRIbelowRa80.
Moderate to poor color rendering properties.
Applications in areas where the quality of color rendering is of minor
importance.
The choice in favor of a particular color rendering class does, of
course, depend on the demands that an application makes on a lamp.
Forexample,aCRIofRa60isinadequateforshoplighting,butis
qualiedasgoodforfunctionalroadlighting.
Indoor_2008_Chapter_12_LIS.indb 10 20-05-2008 14:32:57
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