What is Color Temperature in LED lighting

　　Color temperature, the unit symbol is Kelvin [K]. The color temperature of a light source is the temperature of an ideal black body radiator that radiates light of comparable hue to that of the light source.

　　The color of the light source is usually represented by the concept of color temperature. When the color emitted from the light source is the same as the black body radiator at a certain temperature, this temperature is called the color temperature of the light source. In the black body radiation, different temperatures have different colors of light. Generally the black body undergoes a gradual change process of red - orange - yellow - yellowish white - white - blue. If the color emitted from the light source is the same as the black body radiator at a certain temperature, this temperature is called the color temperature of the light source. The higher the temperature of the black body is, the more the blue spectral components and the less the red components. For example, the color of the incandescent light is warm white and its color temperature can be described as 2700K, and the color temperature of daylight fluorescent is 6000K.

　　Color temperature is defined by an ideal black body radiator. When the radiation of the light source in the visible region is identical with the ideal black body radiator, the temperature of the black body radiator is the color temperature of this light source. Low color temperature light source is characterized by the more red radiation in energy distribution, which is often referred to as "Warm "; when the color temperature increases, the proportion of blue radiation also increases in the energy distribution, which is often referred to as "cold." Some color temperatures of the commonly used light sources are as below: standard candle flame is 1930K (Kelvin temperature units); incandescent lamp is 2760-2900K; fluorescent lamp is 3000K; flash lamp is 3800K; midday sun is 5400K; electronic flash lamp is 6000K; blue sky is 12000-18000K. Kelvin believe that if a black body can absorb all the heat landed on it with no loss and all the energy generated from heat can be transformed into "light" , it will change into different colors due to the different level of thermal received. For example, when the black body is subjected to a heat equivalent to 500-550 ° C, it becomes dark red; to 1050-1150 degrees, it becomes yellow......Thus, the color components of the light source are corresponding to the heat the black body suffered, but expressed with Kelvin color temperature (K) instead of Celsius temperature units. In the process of forging iron, the black iron gradually turns red inside the furnace, which is the best example of the black body theory. When the heat on the black body is enough to release the entire visible lights on the spectrum waves, it becomes white. Generally the tungsten filament inside the bulb is equivalent to the black body. Color temperature calculation method is based on the above principle, using K to represent the color temperature of the light emitted by the heated tungsten filament. According to this principle, any light color temperature is equivalent to the heat temperature of the above mentioned black body suffered. Color is actually a psychological effect on physical. All color images produced are due to intermittent spectral responses in the eye, so the color temperature is only used to represent the color of the visual impression.

　　The selection of LED lighting is often related to the selection of color temperature because different color temperatures have different photochromics:

　　Color temperature below 3300K tends to be red in color, which casts a sedate and warm feeling;

　　Color temperature between 3000K and 6000K is called “neutral” because people have no obvious visual psychological effect and have a refresh feeling;

　　Color temperature exceeds 6000K is bluish in color, which gives a cool feeling.

　　a. color temperature and brightness: when people exposed to light with high color temperature, if not with high brightness, there is a an atmosphere of yin to the people; under low color temperature, if the brightness is too high, people will have a feeling of stuffiness.

　　b. comparison of photochromics: if using two lights with great differences on color temperatures in the same space, the level of contrast effect will occur.

　　Using low color temperature will make red have a bright sense;

　　Using neutral color temperature will make blue have a cool feeling;

　　Using high color temperature will make the object have a cold feeling.