- Mobile: 13723487970
- Tel: (0086)-755-86354829
- Call Me:
Lina
Categorizing different lighting/Light Source
Categorizing different lighting
The color temperature of the electromagnetic radiation emitted from an ideal black body is defined as its surface temperature in Kelvin, or alternatively in mireds (micro-reciprocal Kelvin).[4] This permits the definition of a standard by which light sources are compared.
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. 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. Thus a relatively low temperature emits a dull red and a high temperature emits the almost white of the traditional incandescent light bulb
Many other light sources, such as fluorescent lamps, or LEDs (light emitting diodes) emit light primarily by processes other than thermal radiation. This means that 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 to human color perception 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.
The sun[edit]
The sun closely approximates a black-body radiator. The effective temperature, defined by the total radiative power per square unit, is about 5,780 K.[5] The color temperature of sunlight above the atmosphere is about 5,900 K.[6]
As the sun crosses the sky, it may appear to be red, orange, yellow or white depending on its position. The changing color of the sun over the course of the day is mainly a result of scattering of light and is not due to changes in black-body radiation. The blue color of the sky is caused by Rayleigh scattering of the sunlight from the atmosphere, which tends to scatter blue light more than red light.
Some early morning and evening light (golden hours) has lower color temperature due to increased low wavelength light scattering by the Tyndall effect. This was especially remarked with the increase in small dust particles in the atmosphere after the eruptions of Mount Tambora, 1815 and Krakatoa, 1883, gave rise to intense red sunsets round the world.
Daylight has a spectrum similar to that of a black body with a correlated color temperature of 6,500 K (D65 viewing standard) or 5,500 K (daylight-balanced photographic film standard).
| Temperature | Source |
|---|---|
| 1,700 K | Match flame, low pressure sodium lamps (LPS/SOX) |
| 1,850 K | Candle flame, sunset/sunrise |
| 2,400 K | Standard Incandescent lamps |
| 2,550 K | Soft White Incandescent lamps |
| 2,700 K | "Soft White" compact fluorescent and LED lamps |
| 3,000 K | Warm White compact fluorescent and LED lamps |
| 3,200 K | Studio lamps, photofloods, etc. |
| 3,350 K | Studio "CP" light |
| 4,100–4,150 K | Moonlight[2] |
| 5,000 K | Horizon daylight |
| 5,000 K | Tubular fluorescent lamps or
cool white/daylight compact fluorescent lamps (CFL) |
| 5,500–6,000 K | Vertical daylight, electronic flash |
| 6,200 K | Xenon short-arc lamp[3] |
| 6,500 K | Daylight, overcast |
| 6,500–9,500 K | LCD or CRT screen |
| 15,000–27,000 K | Clear blue poleward sky |
| These temperatures are merely characteristic; considerable variation may be present. | |
Prev: Specialist Areas-Color Matching/Assessment
Next: The types of D65 Lights (6500K)