Colour and greyscale (black and white) pictures look different to us, but it is not clear whether the difference in appearance is a consequence of the way our visual system uses colour signals or a by-product of our experience. In principle, colour images are qualitatively different from greyscale images because they make it possible to use different processing strategies. Colour signals provid...

Colour constancy is the capacity of visual systems to keep colour perception constant despite changes in the illumination spectrum. Colour constancy has been tested extensively in humans and has also been described in many animals. In humans, colour constancy is often studied quantitatively, but besides humans, this has only been done for the goldfish and the honeybee. In this study, we quantif...

BACKGROUND AND AIMS Flower colour varies within and among populations of the Rocky Mountain columbine, Aquilegia coerulea, in conjunction with the abundance of its two major pollinators, hawkmoths and bumble-bees. This study seeks to understand whether the choice of flower colour by these major pollinators can help explain the variation in flower colour observed in A. coerulea populations. ME...

We use the Fourth Data Release of the Sloan Digital Sky Survey to investigate the relation between galaxy rest frame u − r colour, morphology, as described by the concentration and Sérsic indices, and environmental density, for a sample of 79,553 galaxies at z ∼ < 0.1. We split the samples according to density and luminosity and recover the expected bimodal distribution in the colour-morphology...

Substrate colour choice can provide a means of predator avoidance through crypsis. We investigated background colour choice in the Pacific treefrog, Hyla regilla, a species that shows a complex colour polymorphism. Individuals from a single population can be fixed in body colour (the nonchanging green or brown individuals) or they can show an ability to change colour between green and brown (co...

a participatory rural appraisal technique (prat) was used to obtain information from 132 randomly selected turkey farmers in two out of four agricultural development zones in kwara state, nigeria. data were obtained on socio-occupational status of farmers, their production objectives, experience, flock structure, management practices, marketing and consumption of turkey eggs. the results showed...

In this paper, common colour models for background subtraction and problems related to their utilisation are discussed. A novel approach to represent chrominance information more suitable for robust background modelling and shadow suppression is proposed. Our method relies on the ability to represent colours in terms of a 3D-polar coordinate system having saturation independent of the brightnes...

Blood oxygenation level is associated with cardiovascular fitness, and raising oxygenated blood colouration in human faces increases perceived health. The current study used a two-alternative forced choice (2AFC) psychophysics design to quantify the oxygenated blood colour (redness) change threshold required to affect perception of facial colour, health and attractiveness. Detection thresholds ...

Sexual selection often promotes the evolution of elaborate colour signals in males, but the importance of sexually selected colour signals remains poorly studied in amphibians. We used reflectance spectrometry to document pronounced sexual dichromatism and dramatic colour change in Bufo luetkenii, a toad that breeds in large aggregations at the onset of the rainy season in Costa Rica. Our obser...

A recent method for recovering a greyscale image that is free from shadow effects is extended such that the recovered image is a colour image, in the sense that 2-dimensional chromaticity information is recovered. First, the effect of lighting change, and thus to a large degree shadowing, is removed by projecting logarithms of 2D colour band-ratio chromaticities into a direction that is indepen...