Evaluation of the reliability of metameric indices using visual assessment

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.