Resources Related To Solar & Lights

Color temperature is a description of the warmth or coolness of a light source.

When a piece of metal is heated, the color of light it emits will change. This color begins as red in appearance and graduates to orange, yellow, white, and then blue-white to deeper colors of blue. The temperature of this metal is a physical measure in degrees Kelvin or absolute temperature.While lamps other than incandescent do not exactly mimic the output of this piece of metal, we utilize the correlated color temperature (or Kelvins) to describe the appearance of that light source as it relates to the appearance of the piece of metal (specifically a black body radiator).

By convention, yellow-red colors (like the flames of a fire) are considered warm, and blue-green colors (like light from an overcast sky) are considered cool. Confusingly, higher Kelvin temperatures (3600–5500 K) are what we consider cool and lower color temperatures (2700–3000 K) are considered warm.

Cool light is preferred for visual tasks because it produces higher contrast than warm light. Warm light is preferred for living spaces because it is more flattering to skin tones and clothing. A color temperature of 2700–3600 K is generally recommended for most indoor general and task lighting applications. Color Temperature is not an indicator of lamp heat.

Because it is the standard against which other light sources are compared, the color temperature of the thermal radiation from an ideal black body radiator is defined as equal to its surface temperature in kelvin, or alternatively in mired (micro-reciprocal degrees kelvin).[1] For bodies other than ideal black bodies, the color temperature of the thermal radiation emitted from it may differ from its actual surface temperature. In an incandescent light bulb the light is of thermal origin and is very close to that of an ideal black-body radiator.

However, many other light sources, such as fluorescent lamps, do not primarily emit light because of the temperature of the source so the emitted radiation does not follow the form of a black-body spectrum. These sources are assigned what is known as a correlated color temperature (CCT). CCT is the color temperature of a black body radiator which in the perception of the human eye most closely matches the light from the lamp. Because such an approximation is not required for incandescent light, the CCT for an incandescent light is simply its unadjusted temperature, derived from the comparison to a black body radiator.