Published On: 2022-05-12/Categories: EN/Tags: , , /

Definition of color temperature

One of the important specifications of LED products is color temperature, which is related to the color characteristics displayed by LED luminaire.

The measurement unit of color temperature is Kelvin (°K), which is originated by Lord Kelvin who found that from the process of beginning to dissolve to reaching the highest temperature, the metal rendered different colors. He recorded the data and generated the specification sheet of color temperature.

Correlated Color Temperature (CCT)

It is expressed in Degrees Kelvin, that is, when the standard black body is heated and the temperature rises to a certain extent, the color of black body begins to change gradually from dark red – light red – clear yellow – white – blue. When the color of the luminaire is the same as that of the black body, we take the absolute temperature of the black body as the color temperature of the luminaire.

Color temperature of common luminaire

Color temperature classification of solid-state lighting by Energy Star 

White light and yellow light are the most common lights marked on the outer box of LED luminaire, which refer to the color temperature. As it is shown in the figure above, the higher the color temperature, the bluer the color is, and the lower the color temperature, the more yellow the color is. White light = 6,500K, yellow light = 3,000K. These two light colors are often seen on the market.

Color rendering index (CRI) is also an important indicator, which is a measurement that describes the ability of a luminaire to render the color of a real object. The higher CRI of the luminaire, the closer its color performance is to the actual light source or natural light. The CRI of luminaire used for photography must be greater than 90. For household indoor luminaire, it is recommended to be CCT: 5000K, CRI > 80.


Difference between warm and cold light

The most common daily light is cold white and warm yellow. White light contains more blue spectrum than warm yellow light. When irradiating, white light will inhibit the secretion of melatonin and make one feel clear. On the contrary, yellow light will not affect the secretion of melatonin, and one will feel more relaxed under yellow light.

Warm light-

The color temperature of warm light is below 3,300K, which is similar to that of incandescent luminaire. The color temperature about 2,000K is similar to that of candle light, which renders more red light and make one feel warm, healthy, comfortable and sleepy. It is suitable for household, residence and places with low temperature. It is better to adjust the luminaire to warm light before going to bed, which will help falling asleep.

Neutral light-

Neutral light is also called cold white. Its color temperature is between 3,300K and 5,300K. Due to its softness, neutral light makes one feel happy, comfortable and peaceful, which is suitable for places such as shops, hospitals, offices, restaurants, canteens and waiting rooms.

Cold light-

Cold light is also called day light. Its color temperature is above 5300K, which is close to natural light. As it is a bright color that makes one focused, it is suitable to places such as offices, meeting rooms, classrooms, drawing rooms, design rooms, library reading rooms and exhibition windows. Using cold light before going to bed will increase the difficulty of falling asleep.

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