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SDCM: color consistency with LEDs

SDCM MacAdam ellipses

The SDCM (Standard Deviation of Color Matching) value describes the color consistency (color location deviation) of light sources using the MacAdam ellipses as defined by David MacAdam.

Overview of color consistency (LED)

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What is LED color consistency?

SDCM: MacAdam ellipses and importance for wallwashing

Uniform and color-consistent wallwashing

The color consistency stipulates how close the actual light color of an LED is to the defined color location. When selecting luminaires, lighting designers should ensure that the color consistency of the luminaires used is as high as possible. This is particularly important when, for example, wallwashing is carried out with several luminaires. On a white wall, even small color location deviations between the luminaires can be noticed. The unitless SDCM value is used to evaluate color consistency.

What does SDCM mean?

CIExy Farbraum mit Planck’schem Kurvenzug und SDCM MacAdam Ellipsen

Depending on the color location and the extent of color deviation with different LEDs, our eyes perceive a deviation in color location either immediately or only very slowly. Deviations at a specific level are no longer perceived.

If areas are drawn around the deviating but unperceived color location deviations for different LEDs of one color temperature on a CIE xy chromaticity diagram, ellipses are created. An ellipse describes the limit of perceptibility of color differences. These ellipses go back to David L. MacAdam, and are thus often called MacAdam ellipses. The size of the ellipses is standardized and their number is communicated via the SDCM value.

Interesting:

The smaller the SDCM value, the lower is the possible deviation of the light color from the color coordinates specified in the technical data of the light source.

All LEDs located in the first ellipse are perceived by the viewer as identical with regard to their color location (SDCM = 1). The LEDs located in the second ellipse and, under certain conditions, also in the third ellipse, are also perceived as the same or very similar. From SDCM = 4, differences are clearly recognized. Since color location deviations cannot be avoided in LED production, manufacturers of high-quality luminaires make sure that the binning of their LEDs complies to an SDCM value as low as possible.