LED Lights At Home

Color temperature has a specific scientific meaning. If you use the term “warm glow of light” to describe a typical incandescent bulb, a color scientist will correct your naive description. Similarly, the description “warm white” for a particular type of LED that mimics incandescent light closely is a misnomer.

The main think you need to know is that color temperature is measured on the Kelvin scale, with lower kelvin temperatures (below, say, 3500 K) being associated with what we laypeople would call “warmer” yellow-tinged shades of light while higher kelvin (above 5000 K)  is “cooler” light with a bluish tint.

Thoroughly confused now? It is probably best to divorce in your mind the concept of temperature as a measure of heat/cold from any color associations.

But it is handy to know that natural daylight is around 5000 degrees, while incandescent lights are around 3800 degrees.

Some LED products provide their color temperature, in which case it is best to look for ones between 3500 – 4000 K. But often they are labeled simply “warm white” which will approximate the yellowish glow of an incandescent light. If you see “cool white”, they will give off a bluish quality of light you probably will consider harsh and unnatural.

Wikipedia, of course, has a full discussion of color temperature and several nice diagrams. If you really want to know what the kelvin scale is and how a temperature scale is applied to light, read it. But here is a quick summary:

The idea of color temperature originated with Lord Kelvin in the 19th century and relates to “absolute zero”, the temperature at which nothing can be colder. Lord Kelvin’s scale involves heating a “black body radiator” to different temperatures and measuring the light emitted.