Evaluation of the reliability of metameric indices using visual assessment

Abstract

Fifty‐five metameric sample pairs were prepared using computer‐predicted recipes from six different colour centres using cotton knit fabric. The colour difference of each sample pair was measured spectrophotometrically and was assessed visually by a panel of observers against a grey scale under three illuminants: reference illuminant D65, test illuminant A and TL84. In general, there was a positive agreement between observers' assessments although there was some variation due to the spread of ages. The results of illuminant‐specific special indices, CMC(2:1), were better than others, which included CIELAB, CMC(1:1), CIE94(1:1:1) and CIE94(2:1:1). In general, the performance of these five special indices was acceptable. The results of illuminant‐independent general indices failed to show any significant correlation. The effect of residual colour difference under the reference illuminant affected the performance of the special indices to a certain degree, but this was not true of general indices.

A New Approach to the Metamerism Phenomenon in the Frequency Domain

“…Metameric indices are used to represent the degree of mismatch under various illuminants. Two types of indices are in use, namely [16]:…”

“…Another formula proposed by Chow [16] is based on weighting the spectral differences with the spectral efficiency function. The index is [17] (4) where v λ is the spectral efficiency function.…”