Poor lighting conditions or luminaires with poor colour rendering properties in the workspace can ensure that the same object’s colours suddenly look completely different in natural daylight.
Depending on the location and visual task, artificial light sources should ensure a correct colour perception possible, as in natural daylight. In many areas, e.g. in jewellery making when processing gemstones or in dental technology when selecting teeth or white balancing, correct colour recognition is critical to avoid unpleasant surprises.
Thus, a decisive quality feature when buying a luminaire is the colour rendering of the light source. The general colour rendering index indicates it, Ra for short, or international CRI (Color Rendering Index).
The value indicates how naturally or faithfully an artificial light source reproduces colours. The reference value for the colour rendering index of LEDs is the sun with a Ra / CRI value of 100.
How is the colour rendering index (CRI) determined?
We determine the CRI values of a luminaire by DIN6169 using 14 different colours. We compare the test colours’ reproduction or perception under daylight conditions and the artificial light source in a test procedure with a spectroradiometer. The smaller the deviations in colour rendering from sunlight, the closer the colour rendering index is to the optimum value of 100.
How is the colour rendering index CRI specified?
Luminaire manufacturers indicate the colour rendering of an LED work lamp in the datasheet with CRI or Ra. Sometimes a “type” is also included in addition to the specification of the CRI, e.g. CRI> 95 (type 97).
Customers often ask us what the indication of the “type” means in connection with the colour rendering? Therefore we want to explain.
Let’s take the example above. According to the manufacturer, the LED modules achieve a colour rendering index of 97. However, slight deviations are occasionally possible in series production. Therefore, in addition to the colour rendering index (type 97), luminaire sellers specify a minimum value they can guarantee in any case.
In our example, the luminaire has a guaranteed CRI of 95 but typically achieves a CRI of 97.
Which colour rendering do I need for which area of application?
Since the colour rendering of a light source not only influences the recognition of colours, but also influences the wellbeing and performance of people, the EU stipulates that a CRI value of at least 80 must be achieved indoors. In some applications, however, practice shows that a much higher CRI value is necessary to achieve the desired result.
Based on many years of experience with customers from various fields of application, we can give the following recommendations for the colour rendering of workplace lighting:
Colour rendering CRI> 90 for the functional areas of initial and final inspection, tooth selection, ceramic and plastic veneering. For all other functional areas, CRI> 80.
Colour rendering CRI > 80 or CRI > 90 for quality control.
Colour rendering CRI> 90 for the processing of precious stones and the production of jewellery. In other areas, CRI> 80.
Colour rendering CRI > 80 or CRI > 90 for colour controls.
Colour rendering CRI > 80.
Colour rendering CRI 80, better CRI > 90.
What is the colour rendering of RMD task lights?
Our RMD task luminaires achieve CRI values between 80 (Typ. 83) and 95 (Typ. 97) (as of March 2021), ensuring natural and faithful colour perception at work.
Our task lights with the highest colour rendering index CRI> 95 (Typ. 97):