Knowledgebase
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What is color temperature and what do the values mean?
Posted by Larisa Bolli on 21 July 2009 10:35 AM
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"The color temperature of light refers to the temperature to which one would have to heat a theoretical ""black body"" source to produce light of similar spectral characteristics. Low color temperature implies warmer (moreyellow/red) light while high color temperature implies a colder (more blue) light. Daylight has a rather low color temperature near dawn, and a higher one during the day. Therefore it can be useful to install an electrical lighting system that can supply cooler light to supplement daylight when needed, and fill in with warmer light at night. This also correlates with human feelings towards the warm colors of light coming from candles or an open fireplace at night. The standard unit for color temperature is Kelvin (K). (The Kelvin unit is the basis of all temperature measurement, starting with 0 k at a temperature of absolute zero. The ""size"" of one Kelvin is the same as that of one degree Celsius.) Some typical color temperatures are: 1500K Candlelight 2680K 40 W incandescent lamp 3000K 200 W incandescent lamp 3200K Sunrise/sunset 3400K Tungsten lamp 3400K 1 hour from dusk/dawn 5000-4500K Xenon lamp/light arc 5500K Sunny daylight around noon 5500-5600K Electronic photo flash 6500-7500K Overcast sky 9000-12000K Blue sky At this place it shouldn't be forgotten that a color temperature value, though expressed as a single number, doesn't describe a simple property. In reality, it only summarizes the spectral properties of a light source. Two light sources with the same light color can differ widely in quality, for example, when one of them has a continuous spectrum, while the other just emits light in a few narrow bands of the spectrum. Some of the qualitative aspects of such a spectrum can be summarized by means of its color rendering index. The above is from http://www.schorsch.com/kbase/glossary/cct.html CIE, refers to three main color temperatures when discussing daylight. They are referred to as D55, D65, & D75. The ""D"" is shorthand for ""daylight."" The color temperatures' CIExy values are: 5000K is 0.345, 0.352 CIExy and D50 is 0.346, 0.358 CIExy. 5500K is 0.332, 0.341CIExy and D55 is 0.333, 0.348 CIExy. 6500K is 0.314, 0.324 CIExy and D65 is 0.313, 0.329 CIExy. 7500K is 0.300, 0.310 CIExy and D75 is 0.299, 0.315 CIExy." | |
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