APPLICATION OF CIE 13.3-1995 WITH ASSOCIATED CRI-BASED COLOUR RENDITION PROPERTIES

Based on the work completed within CIE Division Reporter 1-68, the Global Lighting Association published a document and an associated calculation tool, that describes the precise procedure for computing the colour rendering indices, Ra and Ri. In addition, the document includes a colour gamut index (Ga) to indicate if the colour gamut of the test source becomes smaller or larger than the colour gamut of the reference illuminant, chroma indices (Ci) to indicate if the chroma of the test-colour samples will decrease or increase (leading to a less or more colourful appearance of object colours), and hi to indicate changes in hue-angle. Together with Ra, the described properties may be useful to objectively explain why object colours can appear differently when illuminated under light sources with similar CCT and Ra values. This paper provides an overview of the CRI-based colour rendition properties and the importance of the accompanying calculation tool.