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Colour Properties of Light Source
Chromaticity or Colour Temperature
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All objects will emit light if
they are heated to a sufficiently high temperature.
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The chromaticity or colour
temperature of a light source describes the colour appearance of the source.
-
The correlated colour
temperature of a light source is the absolute temperature, in Kelvin (K), of a
black-body radiator, having the same chromaticity as the light source.
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Sources with low colour
temperatures - below 3,000 K have a reddish or yellowish colour, described as
warm colour.
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Sources with high colour
temperatures - above 4,000 K have a bluish colour, described as cool colour.
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Warm colour is more acceptable
at low lighting levels and cool colour at high lighting levels.
The colour description and application is summarized as
follows:
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Below
3,000 K warm reddish lower lighting levels
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Above
4,000 K cool bluish higher lighting levels.
Colour Temperature of Common Light
Sources
|
Light Source |
Colour Temp (K) |
Description |
|
Sky -
extremely blue |
25,000 |
cool |
|
Sky -
overcast |
6,500 |
cool |
|
Sunlight at noon |
5,000 |
cool |
|
Fluorescent - cool white |
4,100 |
cool |
|
Metal
halide (400 W, clear) |
4,300 |
cool |
|
Fluorescent - warm white |
3,000 |
warm |
|
Incandescent (100 W) |
2,900 |
warm |
|
High
Pressure Sodium (400 W, clear) |
2,100 |
warm |
|
Candle
flame |
1,800 |
warm |
|
Low
pressure sodium |
1,740 |
warm |
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