Understanding Colour Binning And SDMC

SDCM is an acronym which stands for Standard Deviation Colour Matching. SDCM has the same meaning as a “MacAdam ellipse”. A 1-step MacAdam ellipse defines a zone colour space within which the human eye cannot discern colour difference. Most LEDs are binned at the 4-7 step level, in other words you certainly can see colour differences in LEDs that are ostensibly the same colour.

Due to the variable nature of the colour produced by white light LEDs, a convenient metric for expressing the extent of the colour difference within a batch of LEDs is the number of SDCM (MacAdam) ellipses steps that the LEDs fall into. If the LEDs all fall within 1 SDCM (or a “1-step MacAdam ellipse”), most people would fail to see any difference in colour. If the colour variation is such that the variation in chromaticity extends to a zone that is twice as big (2 SDCM or a 2-step MacAdam ellipse), you will start to see some colour difference. A 2-step MacAdam ellipse is better than a 3-step zone, and so on.

So for example, our ProStrip120 DBX offers a <3-step SDCM, which means it will be much more consistent (and expensive) than standard ProStrip which has an SDMC of between 5&6. To mitigate the potential difference we are now providing BIN codes on our packaging - this means that all strip with that bin should have the same colour but if you mixed strip from different bins then there could be a difference and the amount of difference will depend on the SDMC of the LED type.