Kirschmann's Fourth Law

Kirschmann's Fourth Law states that the magnitude of simultaneous color contrast increases with the saturation of the inducing surround, but that the rate of increase reduces as saturation increases. Others since Kirschmann have agreed and disagreed. Here we show that the form of the relationship between simultaneous color contrast and inducer saturation depends on the method of measurement. Functions were measured by four methods: (i) asymmetric matching with a black surround, (ii) asymmetric matching with a surround metameric to equal energy white, (iii) dichoptic matching, and (iv) nulling an induced sinusoidal modulation. Results from the asymmetric matching conditions agreed with Kirschmann, whereas results from nulling and from dichoptic matching showed a more linear increase in simultaneous contrast with the saturation of the inducer. We conclude that the method certainly affects the conclusions reached, and that there may not be any "fair" way of measuring simultaneous contrast

The temporal factor in apparent transparency

The psychophysical measurements of apparent transparency in function of exposure time, by four observers using the magnitude estimation method, show a loss in intensity of the phenomenon at both ends of the scale (.150 sec and 12.8 sec). The results are briefly discussed in relation to data on the minimal duration and the extinction of some other perceptual structures.Hambrouck Micheline. The temporal factor in apparent transparency. In: Bulletin de la Classe des sciences, tome 73, 1987. pp. 354-359

Etude psychophysique des contrastes chromatiques simultanes.essai de quantification colorimetrique des relations entre couleurs inductrice et induite.

Thèse de doctorat -- Université catholique de Louvain, 197

Perceptual and cognitive factors in the apparent transparency phenomenon

The apparent transparency phenomenon, which is partly linked with cases of figural completion, can be obtained experimentally in well-defined spatio-temporal conditions, when a surface in motion passes behind another physically opaque and homogeneous surface under achromatic illumination. Apparent transparency being poorly coercive in naive observers and requiring a certain degree of cognitive preparation, three series of experiments were devised in order to determine the respective influence of perceptual centration, of verbal information and of repetition on the frequencies of responses reporting the effect. Two pilot experiments allowed the authors to elaborate a response procedure fitting the requirements of perceptual centration without any cognitive interplay of the experimenter. The three experiments proper show the primordial role played by verbal information in this kind of perceptions. Apparent transparency is much less coercive than a comparable case of physical transparency, even when language is used during the experiment. This relatively low Pragnanz of the phenomenon is interpreted in terms of selective attention and of errors in the encoding and in the memory storage of phenomenal data. These two latter factors bring the observers to shift to the Tunnel effect which is more coercive and closer to ordinary perceptual experience.Anglai

Coloured shadows described in a cone contrast space

Two effects which can modify the appearance of a colour seen in a context compared to isolation are chromatic induction and colour constancy. These effects transform colour in ways which depend on the visual system rather than physical characteristics of light and surfaces. They need not reflect different processes within the visual system, indeed, chromatic induction has been attributed 10 the same processes as those involved in constancy, or, as an error of the visual system attempting to achieve constancy. This hierarchy is not necessary: both constancy and induction may result from the same processes without requiring that one promotes the other or that constancy is a goal of the visual system. This study examines induction in terms of cone contrasts in a coloured shadow display, part of a study to establish a relevant measure of contrast and its role in chromatic induction and colour constancy