Why White LED have Different Color Even They have The Same Color Temperature?

In the white SMD LED or white through-hole LED, when it cmes to color temperature, people only care about "yellow light LED", "white light LED", "pure white led", "warm light LED" or "cool light LED" ect, not about the problem of light color deviation. But the ture is, there have much more color in white LED. Even for the same batch of SMD LED or through-hole LED.

People always promise that they will kee their LED have the same color, even the white LED can make sure they have the same color temperature and the color deviation range is within ±150K. (It's report that it won't be found by naked eyes as long as the color deviation range within ±150K). But the real thing is, you still can found the different even there just have little different.

There have two different concept:

Colour temperature
The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of a color comparable to that of the light source.

Correlated Colour Temperature
The correlated color temperature (CCT) is the temperature of the Planckian radiator whose perceived color most closely resembles that of a given stimulus at the same brightness and under specified viewing conditions.

The longitude and latitude on the map represent the location of the city, and the (x, y) coordinate values on the color coordinate map represent the location of a light color. Look at the picture in the top, (0.1, 0.8) this position is pure green, (0.7, 0.25) this position is pure red. There have a white zone on the middle of the picture , this "white zone" can not be described in words, so there is the concept of "color temperature".

Our earliest tungsten bulb, no matter how it is made, its light color can only fall on the line representing cold and warm white light (thick black line in the picture). We call the light color at different positions on this line "color temperature". Now with the development of science and technology, the white light and color we make may not fall on this line. We can only find a "nearest" point and read the color temperature of this point, which is called his "Correlated Colour Temperature".

Generally speaking, the color temperature of the purchased lamp is the Correlated Colour Temperature, such as 3000K. It is not a point on the chromaticity diagram, but several areas (BIN areas) divided by the manufacturer according to the color coordinates, and the color difference of these areas is larger than the area that can be distinguished by the human eye. Therefore, different products Although the nominal color temperature is the same, if they use LEDs with different color temperature bin, it may cause color inconsistency. This is why in some engineering projects or occasions with high requirements for consistency, the lamp manufacturer will use the LED of the specified bin to produce or install only the same batch of products in the same installation area.

Do you get it? If more question about White SMD LED or White Through-hole LED, just feel free to contact us!