What is Color Temperature?

by Andy on February 15, 2012

Daylight Company Lamp In recent years, ergonomics in the workplace has become a large deal as people try to keep themselves as comfortable and productive as possible. One important factor is the color temperature of the light around your workspace. Having the correct color temperature for your task lighting helps reduce eye strain as well as ensure that you see colors properly.

How do we measure color temperature?

Color temperature is intricately related to the concept of black body radiation. An ideal black body is an object that absorbs and radiates all wavelengths of light. This means that it perfectly absorbs all energy given to it, and it perfectly emits the energy it contains. When a black body is heated, it gives off light and when the temperature of the black body and the color of the light source are identical, you get color temperature.

Because color temperature is related to the temperature of a black body, it is measured in kelvins. The Kelvin scale is similar to Celsius, but with 0 situated at the absolute coldest temperature possible, rather than at the freezing point.

Black bodies are theoretical, but there are a few items that closely approximate their characteristics. One in particular is the filament in a tungsten light bulb. Typically the color temperature and the actual temperature of the filament are the same.

However, not all light sources are even close to perfect absorbers or emitters. Some light sources only emit certain wavelengths of light, or they emit some wavelengths more than others. For these the normal color temperature does not work well, as it assumes that all wavelengths are equal. Correlated color temperature is used in these instances by averaging the wavelengths and trying to match it as closely as possible to an incandescent light source. Then you can use the temperature of the incandescent light to find the color temperature.

What are the temperatures of common light sources?

The typical range of color temperature spans from 1,000 kelvins to 10,000 kelvins. At the bottom end of the spectrum is candlelight and other deep red lights. On the other end are blue lights, such as clear skies on bright summer days.

The general colors for these light ranges have an effect on what you can easily see in those lights. For red lights in the 1,000 range, it is much easier to see red colors, making it hard to tell the difference between blues and blacks. Of course many of you may have already noticed that if you are putting on socks and shoes with dim incandescent lights it can be nearly impossible to tell black socks from blue. On the other hand, if you have a very high light color temperature then reds and oranges start to look the same.

When looking for light for a home or work area, you need to find the best temperature to correctly see colors and reduce eye strain. It is typically recommended to have white lights similar to daylight, around the 6,000-6,500 kelvin range. This is a good middle of the road option, especially useful for jobs where you need to accurately see color for design purposes.

For more information on color temperature, you can check out the Daylight Company’s information section. Konica Minolta also has rather extensive resources on both color and light, including color temperature. Make sure to check out the task lights and replacement bulbs available on All-Spec Industries’ main site for your workplace lighting needs.

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