Cite as:
Jurkutaitis M, Kulikowski J J, Zarambaite L, Vaitkeviius H, 2000, "Cone excitation ratios fail to explain colour appearance when adaptation is prevented" Perception 29 ECVP Abstract Supplement

Cone excitation ratios fail to explain colour appearance when adaptation is prevented

M Jurkutaitis, J J Kulikowski, L Zarambaite, H Vaitkeviius

Cone excitation ratios between a test sample and a background are said to determine colour appearance when illumination changes slowly, allowing adaptation.

We devised three experiments demonstrating a gradual failure of this explanation. Munsell samples (value 7, chroma 4) and a neutral background (N7), which was isoluminous with the samples under illuminant C, were simulated on a Barco Calibrator. Eight variable illuminants were used; each illuminated a sample on the background for 1 s. Subjects had to memorise the colour of a sample and matched its appearance by adjusting hue, saturation, and luminance of the reference sample on the background, under standard illuminant C; the matching time was not restricted (asymmetric sequential colour matching).

Real test samples on a neutral background are not isoluminous when illuminated by a variable non-neutral illuminant; in experiment 1, samples were also surrounded by an annulus (looking like real Munsell chips); no annulus was present in experiment 2. Colour matches poorly correlated with cone excitation ratios. In experiment 3, all samples and backgrounds were made isoluminous; subjects could still match colours, but the correlation with cone excitation ratios was poorest. We conclude that only the first stage of colour constancy may rely on cone excitation ratios.

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