Colour difference evaluation in different media

Colour difference evaluation is an important quality control task for the surface colour industries. It has been carried out by visual assessments of surfac7samples by the experienced colourists. However, many viewing parameters such as sample' size, sample separation, textures could have an impact on the perceived colour differences. Recently, evaluations have also been' performed using self-luminous colours to achieve quick response for modem business. Large difference in the viewing conditions between the surface and self-luminous media could also affect the final decision for judging colour difference. This study was divided into two parts according to the different media used, surface and self-luminous (CRT) colours. The goal was to investigate various parametric effects for assessing colour differences including medium, texture, sample separation, sample size, and background colour. Experiment 1 included 107 cotton pairs corresponding to five colour centres. The average colour difference of the sample pairs was about 5 CIELAB units. The grey scale method was used for scaling colour differences with a panel of 10 observers (two assessments for each observer). In general, the parametric effects found were small varying from 8 to 15% except for the background effect, i.e. 42% and 26% for green sample pairs assessed against a green background and the blue samples pairs against ..' a blue background respectively. The results clearly indicate a chromatic crispening effect. Experiment 2 included six phases which reproduced the colours in Experiment 1 onto a CRT. The results confirmed that all the parametric effects found in Experiment 1 and the most obvious effect was the chromatic crispening effect. It was intended to compare results between Experiments 1 and 2 to reveal the difference between surface colour and self-luminous colour under various parametric conditions. The results showed that all CRT colour pairs appear about 20% smaller colour difference than surface colour pairs.