Definition

Colour temperature is the colour value emitted by a light source, expressed in Kelvins.

Introduction

Different light sources produce different coloured light. These different colours can be expressed using a number, and this number is known as the colour temperature.

This video by Phillips Lighting provides a good explanation of colour temperature:

As explained in the video:

When a solid body is heated, it emits visible radiation. The colour of this light is determined by the temperature of the object. This dependency is used to quantify the white tone of lamps. This so called "colour temperature" is used to objectively describe the white tone of a light source and is expressed in Kelvins, the standard unit of temperature.

This video provides a longer and more in-depth overview of the science and psychology behind colour temperature:

Related terms

References

"What is colour temperature?" Photographymad.com. http://www.photographymad.com/pages/view/what-is-colour-temperature. 

Wikipedia contributors, "Color temperature," Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Color_temperature&oldid=817900849 (accessed January 12, 2018).

http://lowel.tiffen.com/edu/color_temperature_and_rendering_demystified.html