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What is CRI?

In the world of lighting, we often encounter terms such as RA value and CRI value. But what do these terms really mean and what are they for? In this article, we dive deeper into the concepts of RA and CRI value and discover their crucial role in assessing color rendering in lighting.

What does CRI mean?

CRI stands for Coloring Render Index, while Ra is used as an abbreviation for Rational Image. Although the two terms have different abbreviations, they refer to the same essential measurement: the color rendering index. This index serves as a measurement tool to determine how accurately a light source reflects the colors of an object. In other words, it assesses how true to life the colors look when illuminated by this particular light source.

What is RA value?

The RA value of a light source is calculated by measuring a (limited) number of reference colors. This average of measurements of these specific colors results in the RA value. However, it is important to realize that this RA value is an average and therefore not fully representative of all colors. This means that even if multiple luminaires with RA values higher than 90 are used, there may still be color differences in the perceived colors of illuminated objects.

CRI and RA value

In practice

When planning lighting for different rooms and applications, a high CRI or Ra value is crucial. For areas where accurate color reproduction is of great importance, such as art galleries, the CRI or Ra value plays a decisive role. By choosing lighting with a higher CRI or Ra value, colors are rendered realistically and naturally. This provides more visual appeal and a more realistic presentation.

The TM30-15 Method

Although the Ra value has long been used as the standard for measuring color rendering, a new and better method is now being applied: the TM30-15 method. This approach provides a more specific understanding of color reproduction by using a wider range of color samples. This is also called the R-family colors This method also gives more detailed information about chromaticity and color differences. Want to know more about this method? Read about it in our article on the TM30-15 method.

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Harry Rijnders

Light Design Manager