Much has been written and said recently about the method used to measure colour rendition or CRI, established by the International Commission on Illumination (CIE). Despite its acceptance at global level, it is becoming obsolete due to the limitations it offers, well-known by the lighting community, as it uses 8 standard colour samples and omits saturated colours.
With the aim of achieving greater accuracy, the Illumination Engineering Society (IES) in the United States has published a technical report which presents a new methodology to measure colour rendition called TM-30-15 that will help identify the most appropriate light source for each application.
This new methodology comprises 3 concepts:
1. FIDELITY INDEX
The Fidelity Index (Rf) is the colour fidelity index. This new methodology evaluates a total of 99 colour samples, while the CRI only uses 8 samples to generate the Ra value. This means that using such a limited series of samples to try to measure the colour rendition results in considerable variations in the reproduction of the visual appearance of an object under artificial light in comparison with natural light. With 99 colour samples, the visual appearance of the object with both light sources is substantially similar.
2. GAMUT INDEX
The Gamut Index (Rg) represents the average saturation displacement of the source compared to the light source of reference. Values of over 100 can be visualised an as increase in the average saturation, while values of less than 100 represent a reduction.
3. COLOUR VECTOR
The Colour Vector is a graphic representation of the colours in relation to a light source of reference.
This method presented by the IES is not a compulsory standard however the TM-30-15 will allow the international lighting community to take steps towards a better standard in the quest for quality illumination.
Alejandro Baselga
Area Sales Manager
