In calculating the color temperature of light sources, you actually use a theoretical model called a BLACK BODY RADIATOR (not a piece of iron). Note that the Black Body is a continuous spectrum source with radiant power at all wavelengths. The chromaticity of the Black Body Radiator at various color temperatures is plotted on the diagram below. Incandescent sources fall on the Black Body line, between approximately 2750-K and 3200-K. Because fluorescent and high intensity discharge lamps do not generate light by means of incandescing, they are not perfectly modeled by the Black Body and do not fall on its line. Therefore, they have a CORRELATED COLOR TEMPERATURE (CCT) indicating the nearest point on the back line as shown.
The color temperature of all the LED products by CREE LLS (CREE LED Revolution blog) actually fall ON the Black Body Radiator line (just like incandescent sources), and so they have an actual Color Temperature, not just a CCT!
Posted by Diane
