Knowledge of white light LED color temperature

Color temperature Definition: When the color of light emitted by a light source is the same as the color of light radiated by a black body at a certain temperature, the temperature of the black body is called the color temperature of the light source.

Because the light emitted by most light sources is collectively called white light, the color temperature or correlated color temperature of the light source is used to refer to the relative whiteness of its light color, so as to quantify the light color performance of the light source. According to Max Planck's theory, when a standard black body with complete absorption and radiation ability is heated, the temperature gradually rises and the luminosity changes accordingly; the black body curve (Black body locus) on the CIE color coordinates shows the process of the black body from red to orange-red-yellow-yellow-white-white-blue-white. The temperature when the black body is heated to the same or close to the light color of the light source is defined as the correlated color temperature of the light source, called color temperature, with absolute temperature K (Kelvin or Kelvin temperature) as the unit (K=℃+273.15). Therefore, when the black body is heated to red, the temperature is about 527℃, that is, 800K, and other temperatures affect the change of light color.

The more blue the light is, the higher the color temperature is; the more red the light is, the lower the color temperature is. The color of the light changes with time during the day: 40 minutes after sunrise, the light is yellower and the color temperature is 3,000K; the sunlight at noon is white, rising to 4,800-5,800K; at noon on a cloudy day, it is about 6,500K; before sunset, the light is reddish and the color temperature drops to 2,200K. The correlated color temperature of other light sources is not an accurate color comparison because the correlated color temperature is actually the evaluation value of the light color performance of the light source when the black body radiation approaches the light color of the light source. Therefore, two light sources with the same color temperature value may still have some differences in the appearance of light color. The color temperature alone cannot understand the color rendering ability of the light source for an object, or how the color of the object is reproduced under the light source.

Correlated color temperature of different light source environments Light source color temperature

Northern clear sky 8000-8500k

Cloudy day 6500-7500k

Summer noon sun 5500k

Metal halide lamp 4000-4600k

Afternoon sunlight 4000k

Cool color camping light 4000-5000k

High pressure mercury lamp 3450-3750k

Warm color camping light 2500-3000k

Halogen lamp 3000k

Tungsten lamp 2700k

High pressure sodium lamp 1950-2250k

Candle light 2000k

Different light sources have different color temperatures, and the light colors are also different. Color temperatures below 3300K create a steady atmosphere and a warm feeling; color temperatures between 3000--5000K are intermediate color temperatures, creating a refreshing feeling; color temperatures above 5000K create a cold feeling. Different light colors from different light sources create the best environment.