SEMANTIC INTERPRETATION OF COLOUR RENDERING INDICES: A COMPARISON OF CRI AND CRI2012

摘要

CIE TC 1-69 recommended a new method (CRI2012) to improve the performance of the current CIE colour rendering index (CRI). In this paper, CRI and CRI2012 are compared on the basis of a semantic interpretation function. Latter function assigns any instrumentally measured colour difference value a semantic interpretation of colour similarity computationally in terms of natural language: very good, good, moderate, low, bad or very bad. A corresponding continuous colour similarity scale (R) ranging between 1.0 (very good) and 6.0 (very bad) is also assigned. The semantic interpretation function results from visual experiments. Computations in this paper revealed that the function R(CRI2012) was linear. This finding verifies the last (re-scaling) computational step of the CRI2012 method. However, the R(CRI) function turned out to be non-linear. This implies that the CRI scale does not represent the human perceptual response. It was also found that the scale of object specific current colour rendering indices was incompatible with the CRI R_a scale.