Thus a relatively low temperature emits a dull red and a high temperature emits the almost white of the traditional incandescent light bulb. An incandescent lamp's light is thermal radiation, and the bulb approximates an ideal black-body radiator, so its color temperature is essentially the temperature of the filament. To the extent that a hot surface emits thermal radiation but is not an ideal black-body radiator, the color temperature of the light is not the actual temperature of the surface. This permits the definition of a standard by which light sources are compared. The color temperature of the electromagnetic radiation emitted from an ideal black body is defined as its surface temperature in kelvins, or alternatively in micro reciprocal degrees (mired). K indicates the color temperature in kelvins, and M indicates the color temperature in micro reciprocal degrees. The vertical axes of Planck's law plots building this animation were proportionally transformed to keep equal areas between functions and horizontal axis for wavelengths 380–780 nm. wavelength (λ) curves for the visible spectrum. The fact that 'warm' lighting in this sense actually has a 'cooler' color temperature often leads to confusion. The spectral peak of warm-colored light is closer to infrared, and most natural warm-colored light sources emit significant infrared radiation. 'Warm' in this context is an analogy to radiated heat flux of traditional incandescent lighting rather than temperature.

Color temperature is conventionally expressed in kelvins, using the symbol K, a unit of measure for absolute temperature.Ĭolor temperatures over 5000 K are called 'cool colors' (bluish), while lower color temperatures (2700–3000 K) are called 'warm colors' (yellowish).

In practice, color temperature is meaningful only for light sources that do in fact correspond somewhat closely to the color of some black body, i.e., light in a range going from red to orange to yellow to white to blueish white it does not make sense to speak of the color temperature of, e.g., a green or a purple light. The color temperature scale is used to categorize the color of light emitted by other light sources regardless of their temperature.Ĭolor temperature is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, manufacturing, astrophysics, horticulture, and other fields. The CIE 1931 x,y chromaticity space, also showing the chromaticities of black-body light sources of various temperatures ( Planckian locus), and lines of constant correlated color temperature.Ĭolor temperature is the color of light emitted by an idealized opaque, non-reflective body at a particular temperature measured in kelvins.

Color temperature conversion chart