You often come across the Color Rendering Index (CRI), or colour rendering index, in a light source’s specifications. This is a value that usually ranges from 70 to 100 and is indicated by the unit Ra. But what exactly does CRI mean? Why is it important? And which value is suitable for your application?

What is CRI?

The colour rendering index (CRI) indicates how accurately the colours of objects are rendered under a particular light source. Imagine this: a red apple looks perfectly red in daylight, but under a green lamp, its colour may look completely different. The higher the CRI, the more realistic and true-to-life the colours appear. This is because CRI depends not only on a lamp’s colour temperature, but primarily on how its light spectrum is composed.

How is CRI determined?

CRI values range from 0 to 100 and are measured by comparing a series of standard reference colours under a specific light source with the same colours under natural daylight. The smaller the difference, the higher the CRI score. A CRI of 100 means that colours are rendered exactly as they are under natural light.

CRI is calculated by comparing eight standard colours under a test light source with their appearance under a reference source, such as daylight or an incandescent lamp. The difference between the colours is averaged, resulting in the final CRI value. The closer it is to 100, the better the colour rendering.

Why is CRI important?

Good colour rendering is essential in spaces where colour plays a role in work or experience. Think of a clothing shop where customers want to see the exact colour of a fabric, a hair salon where hair colours need to be assessed accurately, or a hospital where doctors need to be able to detect colour differences in the skin. In these situations, a low CRI can lead to incorrect assessments and less accurate results.

Applications where CRI matters

• Retail: Products are displayed in their true colours, contributing to better presentation and purchasing decisions.

• Healthcare: A high CRI is essential for accurate medical diagnoses and treatments.

• Art and photography: Colour accuracy is crucial when displaying art and taking photographs to capture true hues.

• Residential: At home, a high CRI provides warm, natural lighting that enhances the visual appeal of the space.

• Industrial applications: Improved task accuracy and safety through a clear and natural representation of colours.

Which CRI values are suitable for different applications?

The required CRI value depends on the application and the importance of colour accuracy:

• CRI 90-100: Ideal for applications requiring the highest colour accuracy, such as art galleries, hospitals and high-end retail.

• CRI 80-90: Suitable for offices, living spaces and general retail lighting.

• CRI 70-80: Suitable for industrial and outdoor lighting where colour rendering is less important.

• CRI below 70: Not recommended for indoor spaces due to poor colour rendering, but suitable for certain industrial or safety environments.

CRI and LED lighting

Modern LED lighting has made tremendous progress and can achieve CRI values above 90, comparable to traditional incandescent or daylight. When choosing LED lighting, pay attention to the CRI score to ensure that it is suitable for the intended application.

How do you choose the right CRI?

Do you want perfect colour rendering in your space? Here are some guidelines:

• Track lighting for home use: A CRI of at least 80 provides warm and natural lighting.

• Track lighting for workplaces: Choose a CRI of 85-90 for offices, so that text and images are clearly visible without causing eye strain.

• For specialised applications: Museums, hospitals and design studios benefit from a CRI of 90-100 for the most true-to-life colour rendering.

Conclusion

The CRI of a light source plays a major role in how we perceive and experience colours. The higher the CRI, the more natural the colours. For general applications, a CRI of 80 or higher is perfectly adequate, while specialised environments are better off choosing 90 or higher. Not sure which CRI is best for your situation? Feel free to contact us for personalised advice!