SDCM stands for Standard Deviation of Color Matching, which is to distinct LED color variation level where the human eye cannot perceive the color difference. It has the same meaning as a “MacAdam ellipse”. It plays an important role in LED technology and output.
The spectrum of the standard light source changes with the color temperature, so the standard spectrum is different when the color temperature is different (generally, the detection equipment will automatically identify the color temperature range of the LED light source to be measured, and determine the corresponding color temperature value of the standard light source), and the color tolerance is different. At the same color temperature, the reference standard spectrum is the same, and the color coordinates x and y are different, then the color tolerance is different.
SDCM defines the tolerance in the color temperature with a number. If the LEDs all fall within 1SDCM (or a “1-step MacAdam ellipse”), the color difference between LED chips cannot be discerned by human eye. 2-3 SDCM means there is hardly any visible color difference while 4 or more SDCM is readily noticeable. The smaller the number is, the smaller tolerance with respect to the XY color space will be. But be noted that it only represents the color comparison under a certain light source, not under different light sources.
Most LEDs are binned at 2-7 step level. For commercial lighting, we typically use 2-3 SDCM now to make sure the consistent stability of lighting.