Juan L. NIEVES^*, Eva VALERO, Javier HERNANDEZ-ANDRES and Javier ROMERO

Departamento de Optica, Facultad de Ciencias, Universidad de Granada, 18071 Granada, SPAIN

(Received December 26, 2002; Accepted May 9, 2003)

We report on experiments in which observers judged colour appearance within the context of time-varying colour adaptation. We used pairs of contextual images consisting of a rapid succession of colour surfaces reproduced under different illuminants to analyse the effect of temporal colour adaptation rather than a spatial context on asymmetric matching and also to judge its influence upon the cone excitation components. We used adaptation colour distributions along the red–green and yellow–blue axes (selective conditions) and random colour distributions (non-selective condition). The results of observers' matches for both conditions showed approximate colour-constant appearance. Although light adaptation did not fully compensate the colour changes, we obtained average colour-constancy index values of 0.6. The results for the two opponent conditions showed similar contextual effects. No significant differences between each condition were found for the L- and S-cone mechanisms and the three test illuminants. On the contrary, some degree of interaction between the comparison-field cone excitations and the colour axis can be seen when the colour mechanisms are analysed separately. This seems to be more pronounced for the S-cone mechanism and suggests that the selective condition of the adaptation sequence may well affect the observer's chromatic matching response.

Key words: colour appearance, colour vision, colour mechanisms, colour constancy, adaptation, vision

^*E-mail address: jnieves@ugr.es