Comparative study of visual colour differences using reflective and self-luminous colour stimuli

In this study, visual colour difference assessments were conducted using both reflective colours which are dyed cotton fabrics with no obvious texture pattern and self-luminous colours displayed on a CRT monitor. All together, eighty-two pairs of colour samples belonging to five different colour centres were used. The average colour difference for all pairs is about 5.0 CIELAB units. The values of the colour difference for the self-luminous colour pairs (ΔEself-luminous) are very close to those of the corresponding reflective colour pairs (ΔEreflective), i.e., the reproduction of the reflective colour pairs onto the CRT monitor was very accurate. Grey scale method was used in the visual assessment of colour difference. The assessments were done using five different viewing conditions, i.e., reference viewing condition recommended by CIE (CIE Technical Report CIE 116-1995), and the other conditions which include a 3-inch gap between samples in a pair, small sized sample corresponding to 2° angle of subtend, and two different background colours. In comparison with the visual colour differences of the reflective pairs under the reference condition, the results obtained from the CRT colour pairs are 15% smaller. Under other viewing conditions, the visual colour differences of the CRT colour pairs are 13 to 18% smaller than those of the reflective colours pairs. Further comparison was made using chromatic colour discrimination ellipses for self-luminous and reflective colours.