Color Rendering Index (CRI) in the LED Lighting

Color Rendering Index is we called CRI, do you know this?

When there is little or no main wave reflected by the object under the reference light source in the light source spectrum, the color will produce obvious chromatic aberration. The greater the degree of chromatic aberration, the worse the color rendering of the light source. The color rendering index coefficient (Kau fman) remains the common method for defining the color rendering of a light source.

The color rendering index of sunlight is defined as 100, and the color rendering index of incandescent lamps is very close to sunlight, so it is regarded as an ideal benchmark light source. This system is tested with 8 standard color samples with medium chroma, and compares the degree of deviation of the 8 colors under the test light source and the benchmark of the same color temperature to measure the color rendering index of the light source, and take the average deviation value Ra20-100 , with 100 as the highest, the larger the average color difference, the lower the Ra value. Light sources below 20 are generally not suitable for general use.

Index (Ra) Rating Color Rendering General Application:
90—100  1A Excellent Locations that require accurate color contrast
80—89    1B / Places where correct color judgment is required
60—79     2 Normal Places requiring medium color rendering
40—59     3 / Places with low requirements for color rendering and small color difference
20—39     4 Poor Places with no specific requirements for color rendering

The theoretical color rendering index of incandescent lamps is 100, but there are many kinds of incandescent lamps in real life and different applications, so their Ra values are not completely consistent, and it can only be said that it is close to 100, which is the lamp with the best color rendering. The CRI values of specific lamps can be seen in the table below.

Light source Color rendering index Ra
Incandescent lamps  97
Daylight color fluorescent lamp 80—94
White fluorescent light 75—85
Warm white fluorescent light 80—90
Tungsten halogen lamps 95—99
High pressure mercury lamp 22—51
High pressure sodium lamp 20-30
Metal halide lamps 60—65
Sodium thallium indium lamp 60—65

Dysprosium lamp Index (Ra) level above 85 Color rendering General application
90—100 1A Excellent Locations that require accurate color contrast
80—89 1B / Places where correct color judgment is required
60—79 2 Normal Places requiring medium color rendering
40—59 3 / Places with low requirements for color rendering and small color difference
20—39 4 Poor Places with no specific requirements for color rendering