Kelvin is one way to measure white light spectral output, but it isn’t technically a measurement of light energy at all. Much like Fahrenheit and Celsius, this is a metric of temperature. Over the years, Kelvin has been adopted by the lighting industry to describe what is referred to as the “color temperature” or hue of a white light source. Color Temperature is based on the rule that a filament or radiator will emit different colors of light depending on the temperature of said filament. The hue shifts from red at lower temperatures to orange, then yellow, then blue.
Encyclopedia
