This article is the second in a series of two articles focusing on the fascinating world behind the science of lighting. This second article gives you a brief insight into how to measure color rendering by using CRI, Ra and CQS. If you want to know more about what is hiding behind these abbreviations, then you should keep on reading!
When it comes to measuring lighting in terms of color rendering there are several different ways to go about it. You might think color rendering is not a big deal, but the color rendering actually has an enormous influence of how things are revealed in a certain environment. Now let’s take a look at three different types of measurements of color rendering: CRI, Ra and CQS
CRI, Ra and CQS
CRI stands for color rendering index and can be defined as a quantitative measure of the ability of a light source to reveal various objects faithfully compared with a natural light source. CRI is described in percent, and the closer to a 100 % the CRI of a light source is the better the color rending. On average, a light source with a CRI above 80 % is regarded as having a good color rendering capacity.
What is the difference between CRI and Ra index then? In short, the difference between CRI and Ra is, that in the Ra index the measurement has basis in the 8 standardized colors but when using the CRI the measurement also includes 6 more colors. Therefore, the CRI is a more detailed form of measurement. Below you see the Ra index.
However, it is important to note that CRI is slowly becoming an older method of characterizing a light source. Therefore, new methods are emerging and challenge the older CRI method. One of the new methods especially worth mentioning is the color quality scale (CQS) which is a modified method of the CRI method. The CQS can, however, solve some of the problems experienced when using CRI and therefore CQS is used more and more by professionals. CQS is especially good for measuring LED light sources because the CRI or the Ra index are not the optimal solutions for measuring this type of light sources. Therefore, the CQS can with advantage be used as an alternative to the CRI or Ra method. CQS is not approved as a standard yet, but a safe bet is that in the near future it will become the standard used when measuring LED.
The picture below shows examples of various CRIs and CQSs in comparison of different light sources used in homes, shops and offices etc. For example, you can see that a warm white LED light source, often used in restaurant and café settings, have a CRI on 81 % which makes it a light source with a good color rendering. On the other hand, fluorescent tubes in cold white only have a color rendering capacity of 63 % which makes this type of light source worse at revealing objects faithfully in comparison with natural light.
If you want to know more about CRI, Ra or CQS you are welcome to contact us in Normasym. We can also advise you on how LED can optimize your lighting and we can help you find a cost-saving and energy-efficient LED solution that will fit you specific need perfectly.