Colour Rendering Index
March 7, 2019
CRI stands for Colour Rendering Index. CRI indexes how faithfully a set of 8 colours (R1-8) are presented by a particular light source, compared to an ideal or natural light source (such as daylight).
The CRI value can vary between 0 and 100, in which 100 equals the ideal light source. The higher the CRI value of the light source, the more accurate the colour representation. Luminaires with high CRI consume the same amount of energy as luminaires with low CRI. The result is qualitatively greater colour quality without any noticeable reduction in light intensity. A light source with a high CRI is particularly important in retail, fresh food and hospitality. The visualisation of colour plays an important role in these sectors.
Quality categories CRI
Within the Colour Rendering Index, there are four different quality categories. The average CRI value of LED lighting lies in the category 80 -90 (Good, colour representation relatively true to nature).
|90-100||Excellent, true-to-life colour representation.|
|80-90||Good, colour representation relatively true to nature.|
|60-80||Moderate, colour representation may differ from colour fidelity.|
|<60||Bad, colour representation differs from colour fidelity. Use where colour representation is not essential.|
CRI and TM-30
The CRI index has a number of crucial shortcomings. The old index (CRI) is based on a limited and outdated colour spectrum. As a result, the index displays limited information. Therefore, the Illuminating Engineering Society (IES) has published a new index, TM-30. In this article, we are referring to version 15 of TM-30. TM-30 does not base the colour fidelity value on 8 rather on 99 colours, including essential colours such as red (R9) and skin colour (R15).
TM-30 consists of two components: RF and Rg. RF is a metric similar to the CRI. Only RF is based on a more extensive colour palette than CRI, namely 99 colours (R1-99) instead of only 8 colours (R1-8). These additional colours cover a wider colour palette, in which saturation, the red value (R9) and skin colours (R15) play an important role. In addition, Rg measures the average gamut shift (tone/saturation) of the source. So, TM-30 based on 99 colours gives a more realistic representation of the authenticity of colours from an LED light source, compared to CRI that does this based on 8 colours.
Future of Colour Rendition
TM30 was adopted to complement and ultimately replace the old CRI (CIE) metric for measuring the reliability of a light source. TM-30 is an improved colour metric that will help to measure the colour representation of numerous light sources, mainly LED lighting, more accurately.
With CRI, the higher score was usually perceived as superior. For TM-30, the best light source depends on the application in which it is used. TM-30 gives users sufficiently detailed information to make that decision accurately. At the end of the day, TM-30 is an important tool that helps the lighting industry to understand and apply colour rendering metrics.
CRI, TM 30 and Illuxtron luminaires
All small LV downlights (1150/1250Lm) are standardly equipped with the latest CRI97 LED from Lumileds. The same CRI97 LED will also be available for large downlights in the second half of 2019. The Crispcolor versions of the LUXEON Stylist series will continue to exist because the spectrum is made in such a way that everything appears even more beautiful. LUXEON Stylist series have been specially developed for stores specialising in fashion, fresh food and restaurants. The LUXEON Stylist Series is compatible with many Illuxtron luminaires.
In our catalogue you can find a comparison list with all values per type of LED.