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 in the CIE 1931 2 deg (xy) 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.
Color difference is an important indicator of lighting lamps color performance. Color difference is the difference between computer calculation forma and the target standard, calculated by single lighting source, the value is smaller, accuracy is higher. Please note, it only represents the compared color of a light source, it can not detect the deviation under different light sources. Generally speaking, color difference refers to the distance that the measurement value deviates from the target value, the difference between the light source spectrum and the standard spectrum. It needs provide the target value and calculation formula to know the measurement value of color difference.
Standard spectrum changes with color temperature, the color difference is different for the same light source if the standard spectrum is different, but when test, general color photoelectric analysis system can automatically identify the color temperature range where the measured light source is, to determine the color temperature value of standard spectrum. When the color temperature is same, reference standard spectrum is consistent, chromaticity coordinate X,Y is different, the color difference is also different.
Color difference unit: SDCM. National standard has its specific testing requirement, IEC 60901 and GB-T17262 single-ended fluorescent lamp performance requirements specified in the standard that general energy-saving lamps require color tolerance less than 5 SDCM. IEC 62717 and GB24823 general lighting for LED modules performance requirements specified in the standard that LED modules require color difference less than 7SDCM. In the ellipse of 5SDCM, color difference is 5 if the point is on the curve of ellipse, color difference is less than 5 if the coordinates is in the circle of ellipse. IEC standard requires that the lamp chromaticity coordinate(x,y) should not deviate the rated value from 5SDCM, that is to say, the chromaticity coordinate of lamp should be in the ellipse, the color difference should be less than 5 SDCM for general energy-saving lamps. For color difference ellipse diagram, outer ring is 6SDCM corresponding to the national standard, inner ring is 5SDCM corresponding to international standard. Industry standard, Energy Star ANSI C78.376, Color Difference≤7SDCM; EU Standard IEC60081, Color Difference≤7SDCM; National Standard GB10682-2002, Color Difference≤5SDCM.
In the fluorescent lamp, as the density of red, green and blue powder is different, it is easy to cause color temperature difference in production. Once appear, it needs adjust color difference to adjust color temperature difference to ensure light color of light. White LED as light source, it should refer to color difference standard requirement to guide the development and application of white LED new lighting source.
The EU standard ERP, in accordance with the explicit technical requirements to regulate the LED division area, SDCM≤ 6. Radians lighting as a led downlight supplier, this dimmable down lights we are able to achieve SDCM<6, in compliance with the new ERP standard.
