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White light surrounds us, and if we pause to look, we will see that the color of white light varies dramatically from warm reddish yellows to cool blue bright whites. While we can all “feel” the quality and nature of white light, it’s typically described with two numbers: Correlated Color Temperature (CCT) and Color Rendering Index (CRI).
CCT is a statement of how warm or cool the light looks. The lower the number, the more yellowish and warm it seems to us. The higher the number, the brighter and cooler it seems. A typical halogen bulb has a CCT of about 3000K (K = Kelvin), and moonlight is approximately 4100K. Xicato tunes its modules to provide light output measured as 2700K, 3000K, 3500K and 4000K.
Color rendering is a measure of how accurately colored objects are rendered when lit with a particular light source.
If we look at the CIE color space often used to define and describe white light, we can see a black line running through the center; this is called the black body locus. As long as the light stays on or about the line, our eyes perceive it as white. If the white light shifts above the line, it will tend to display a green tint; if it shifts below the line, it will display a pink tint. The measurement of visible difference is described as a MacAdam Ellipse.
In general, a shift of 1 MacAdam Ellipse (1 step, or 1 SDCM) will not be noticeable to the human eye, and if the shift is along the black body locus, it’s generally not noticeable for 2 steps, or 2 MacAdam Ellipses. Once the white color has shifted 3 steps, the change can be detected by the human eye, and Xicato believes this represents the end of life of an LED or LED module. You can find more details on our Color Consistency page.
Xicato ensures that all of its modules are manufactured to a very tight tolerance for white light, an area that measures 1 step by 2 steps. Most of the industry defines tolerance as within a 3-step area, which is more than 3 times larger than the Xicato area. When it comes to white light control, some say that Xicato ends where others begin.