What is the colour rendering index (CRI) and why is it so important?

By: Secom
14 de March, 2023
Reading time: 5 min

The colour rendering index, or CRI, is a measure of the quality of light emitted by luminaires. It can help us choose the right kind of light fixture for a huge range of sectors, from healthcare right through to tourism.

En este artículo trataremos...

  • What is the colour rendering index?
  • How is the colour rendering index calculated?
  • Why the colour rendering index is important and where it has most impact
  • SECOM adaptable lighting

What is the colour rendering index?

The colour rendering index tell us if the colours in a device light spaces up in a manner that faithfully resembles the colours in that space when they are lit by sunlight. The index works on a scale of 1 to 100, where 100 is the best possible score. It means that devices with a CRI score below 80 do not render colours well.

But why is it important to work out the CRI score and understand what it means? The CRI is especially important in certain lighting projects for spaces in which the appearance of items needs to be as realistic as possible. For example, in hospitals, restaurants and food shops, among others. In these places, it is absolutely crucial for us to see exactly what items such as flesh, meat, fish or fruit really look like. If not, we could easily miss things like bruises, haemorrhages and decaying food.

We most definitely need systems with a CRI score in excess of 80 or even 90 if we want to see these kinds of details. These CRI values help us perceive colours exactly as they are, while lower values mean there are significant variations in definition. When the CRI is just right, it can even have important consequences such as decreasing incorrect diagnoses in hospitals.

How is the colour rendering index calculated?

We have some simple means of calculating the colour rendering index. One of them entails comparing what a sample looks like under artificial light with what it looks like in natural light. Alternatively, we can use a standardised object as a reference.

For temperatures up to a maximum of 5000K, we use a black-body radiator. For figures in excess of this, we use daylight. Whatever the option, we can use these figures to work out an average score that gives us an idea of how precisely colours are rendered. This is why it is not correct practice to link the CRI and light spectrum of a luminaire. In fact, several devices can have the same index score but present different results because other features in those devices are not equal.

What we can say for sure, however, is that if we want to get optimum CRI lighting results, LED technology lights are undoubtedly the way forward.

Why the colour rendering index is important and where it has most impact

The usefulness of the CRI is particularly evident in certain professional or domestic scenarios in which we need to be able to see as well as possible. This includes places such as the restaurants, hospitals and food shops mentioned above. The range of places is huge, but they all have one thing in common: the need to faithfully reproduce objects under artificial light. Here are some examples:


Whether we are talking about homes or industrial facilities, kitchens are places in which we need to see colours well. The more realistic the colours, the better we can handle and prepare food. If we have an LED light with the right values, it can help us see if food is fresh or if it going off.

Clothes shops

It is easier to choose clothes in a shop if we can get a good idea of what those items look like in daylight. It gives us a good idea of exactly what the item of clothing we are thinking of purchasing is like because we can see all its features.

The tourism sector

Tourist spots and hotels need to plan their lighting well so that colours are lit in such a way that they have the desired impact. The sector tends to focus on relaxation, comfort, well-being and so on. Therefore, if we select products with a high index result, we get the ambience we are looking for.

Entertainment and culture

At exhibition centres and entertainment venues, the CRI score should be high. What we are aiming for in these establishments is to display works of art and creations in their most natural form, without any alterations.

Street lights

In certain places, we have to prioritise an elevated luminous flux over the CRI. That is, we aim for many lumens per luminaire. Other aspects, meanwhile, can appear somewhat distorted. Tunnels are good examples of this because of how important it is to see vehicles clearly. The smaller details, however, are far less crucial. This can also help us increase our energy savings.

SECOM adaptable lighting

Once we have a good grasp of the CRI of an LED light, it is easier for us to choose the right luminaire for our project. These are just some examples of the luminaires that SECOM has on offer:

  • BAMA wall light. The angle at which light is emitted and the intensity of that light can be adjusted on this luminaire to create an inviting and attractive ambience. Since it has an IP54 resistance level, we recommend using it outdoors.
  • Innvictum Sport. This luminaire is one of the best spotlights for sports facilities. It has an intensity adjustment feature and it can be positioned at different angles.
  • Loop. This indoor downlight has a high CRI score and is ideal for business premises, homes and industrial buildings.

In short, the colour rendering index is a key indicator for lighting projects, particularly in certain spaces with specific requirements. If we use the index correctly, we can be sure that the colours in our environment or activity are represented in just the right way.

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