Colour Rendering Index Explained

Because Sun is our main light source, researchers use daylight as a benchmark to compare the colour of the artificial lights. The highest possible CRI value is 100 and would be given to sunlight. The CRI is a scale from 0 to 100 to measure colour rendering light quality, although some lights, like the sodium-vapour lamps, has negative CRI.


Calculating CRI

The higher the CRI, the better the rendering colour accuracy and the colour that you are looking under the artificial light is closer to the ideal source of illumination for good colour. The newest method to test the CRI is R96a method, with new features like new chromatic adaptation transform (CIECAT94) or adaptation of all colours to D65, although the main feature is that the CRI is averaged to 10 (R10), not 8 colour samples like before (R8), to give better results in testing the colour difference. These are the general colour samples that scale from R1 to R10, but many companies with high CRI values, like Lightcraft, are testing their lamps from R1 to R15, which includes test colour samples like Saturated Red (R9), or skin colours (R13 and R15). 

Colour Rendering Index - Ra



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