Difference between Ra and CRI

Difference between Ra and CRI

As we know the white color is a mixed color and including most of the spectrums, when we evaluating the quality of white color, we always compare the LED light to the Sun Light. The sun light is the standard.

There are 15 color samples included in the white color, we test the intensity of each sample compared to the sunlight. The 15 samples as following:

Then comes to the difference of the Ra and CRI:

Ra = Average(Sum(R1:R8))

CRI = Average(Sum(R1:R15))

Although CRI is covering more spectrums and more accurate, the Ra is still the besting popular standard in the markets now. Most of the light testing equipment can easy to get the value of R1 to R15, however, the final result Ra is specified. For example:

The Ra=97.2 is the average of R1 to R8.

Special R9?

R9 is the 'strong red', which normally merely included in white color, because the more the red the harder to control the color consistency and color temperature. So, many LED Supplier has a poor testing result on R9. If the Ra > 70, is good; if Ra > 90, is perfect.