CRI - Colour Rendering
The measure of light quality
The internationally recognised colour rendering index Ra (CRI) was defined in order to objectively assess the quality of light sources. The evaluation method is defined in the international standard CIE 13.3 from 1995 and is valid worldwide. In the assessment, 15 selected test colours are used to compare the test light source with a standardised reference light source. The rating scale is between +100 and -60. The better the colour fidelity of the test light source, the higher the colour rendering value. However, this method only assess colour fidelity - colour saturation is not taken into account.
What is the difference between Ra and Re values?
The colour rendering index Ra (general reference) is calculated from the mean value of the first 8 test colours (R1 - R8). The minimum requirement of the EN 12464-1 lighting standard stipulates a colour rendering of Ra ≥ 80 for most activities. This is why many lighting systems are only designed with this light quality. The values of the test colours R9 - R15 are not included in the calculation of the Ra. However, these values provide detailed information on the colour fidelity of the saturated colours (R9 - R12), the skin colour (R13), leaf green (R14) and the Asian skin tone (R15). The average value of all 15 test colours is expressed by the Re value( reference extended) and enables a more precise evaluation of the light quality. Especially in high-quality retail environments and for medical examinations, the Re value is more meaningful than the Ra value.
Bar chart for better comparability
As the minimum requirement is Ra ≥ 80, XAL has set the baseline of the colour fidelity values to Ra 80. This makes the differences between Ra 80, Ra 90, Ra 95 and Ra 99 more clearly visible. Based on school grades, you will also find our assessment of light quality in the charts.
sufficient
good
very good
very good
Lighting quality in the retail sector: How CRI 95 makes the difference
What this means for applications in the retail sector is explained here. While colours appear pale at CRI 80, they appear much more intense and with a higher contrast at CRI 95 with the retail lighting colour VOGUE which we recommend. Due to the high colour fidelity and saturation, illuminated products in the shop appear even more vivid and attractive. In addition, the strong, natural colours have a positive emotional effect on customers.