A Methodology for the Prediction of Complementary Colours in Chromatic Afterimages

Abstract

The colour of chromatic afterimages is usually discussed as the inversion of the complementary hue without specifying clarity and chroma. After steady and prolonged perception, colours lose their initial strength due to a partial adaptation of the visual receptors. Under these circumstances the appearance of colours tends toward a neutral point, an achromatic grey equidistant to black and white. If the gaze is then directed towards a white or grey surface, the previous loss of chroma causes the complementary tone. To precisely determine the tone, clarity and chroma of afterimages seen on an achromatic surface, a model using equalisation tests compares their effect with an appropriately chosen sample colour. In many cases, after 20 seconds of fixed perception, the comparison sample results in a colour of complementary additive tone with a saturation of half the original sample and an inversion of clarity equivalent to the loss or gain in the adaptation colour. For this comparison sample to be reliable, it should not be affected by the border colour of the original sample. To this end, a medium grey that does not create an afterimage on the comparison sample is juxtaposed. The study shows that reds and greens give the expected results. However, yellows and blues give afterimages that deviate toward purples and oranges. The more saturated the yellows and blues are, the more severe is this effect.