Color Temperature: when the color of the light source is the same with that of the black body under a certain temperature, the temperature of the Black body is called the Color Temperature ( Color Temperature Meter ).
As most light given by light source is called white light, the color temperature or the related color temperature is used to indicate the white extent of the color temperature, which was showed by the quantized light source. According to the theory of Max Planck, if a standard black body with the complete ability of absorption and radiation is heated, the luminosity will change with the gradually increasing temperature. The black body locus on the color coordinates of CIE shows that the color of the black body changing from red to orange lake and then yellow, yellow and white, white and blue white. Heating the black body until its temperature is close to or the same with that of the light source, then we can call the related temperature as the color temperature, measured with the unit of K (Kelvin, k=℃+273.15). Therefore, the temperature of the black body when it heated red is about 527℃, namely 800K. However, other temperature can also influence the change of the light color.
The light color is more inclined to blue, the color temperature is higher; while it is more inclined to red, and the color temperature is lower. The light color changes over the time in a day: within 40 minutes after the sunrise, the light color is yellow, the color temperature is 3000 K; At noon, the sunlight is white, the color temperature rises to 4800-5800 K; At noon in a cloudy day, it is about 6500 K; Before sunset, the light color is more red, the color temperature drops to 2200 K. The relevant color temperature of other sources may have some differences on appearance, because the relevant color temperature in fact is the performance appraisal value of the light source and the light color when the black body radiation is close to the light source and the light color, but is not a precise color contrast. Therefore, the two light source of the same color temperature value possibly still has some differences on the appearance of the light color. Only by the color temperature, we can’t understand the color rendering ability of the light source on the object, or the representation of the object color under this light source.
The color temperature of the relevant temperature of the light source in different situations
Sunshine in the north part: 8000K-8500K
Cloudy day: 6500K-7500k
Temperature at noon in the summer: 5500k
Metal halide lamp: 4000K-4600K
Sunlight in the afternoon: 4000k
Cool color fluorescent lamp: 4000k-5000k
High Pressure Mercury Lamp: 3450-3750k
Warm color fluorescent lamp: 2500-3000k
Halogen lamp: 3000k
Tungsten lamp: 2700k
High voltage sodium lamp: 1950-2250k
Candle light: 2000k
The light color is different with the difference of the light source color temperature. The color temperature below 3300 K has a sedate atmosphere and warm feeling; the color temperature in 3000- 5000 K is the middle color temperature, and has the pleasantly cool feeling; the color temperature above 5000 K has cold feeling. Different light color of different light source can produce the best environment.
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