Search results for "Color perception"
showing 10 items of 71 documents
Implementations of a novel algorithm for colour constancy
1997
AbstractIn agreement with the principles of the relativistic model proposed by Creutzfeldtet al., with the photometric rule (lightness anchoring rule) and with the influence of simultaneous contrast in the appearance of a visual scene, we propose a first-stage mechanism yielding substantial colour constancy. We have defined a set of first-stage colour descriptors, and to test their utility, we have performed a simulation using a Machine Vision System (MVS). The statistical stability of the descriptors for Munsell samples under different illuminants is good.
Multichannel functional testing in normal subjects, glaucoma suspects, and glaucoma patients
2012
Purpose.: To evaluate visual function with a novel multichannel functional test named the ATD Multichannel Functional Test. Methods.: This multicenter study had a prospective and cross-sectional design. A total of 186 eyes were included: 42 with glaucoma, 14 glaucoma suspects due to optic nerve characteristics, 25 ocular hypertensives, and 105 normal eyes. All patients performed standard visual fields (Humphrey 24-2) and ATD with eight stimuli configurations: four achromatic (A), two red-green (T), and two blue-yellow (D). To derive main outcome measures, mean sensitivity, mean defect (MD), and pattern standard deviation (PSD) were calculated and compared among groups and types of stimuli w…
A field test of behavioural flexibility in Zenaida doves (Zenaida aurita).
2010
7 pages; International audience; Animals' ability to adjust their behaviour when environmental conditions change can increase their likelihood of survival. Although such behavioural flexibility is regularly observed in the field, it has proven difficult to systematically quantify and predict inter-individual differences in free-living animals. We presented 24 Zenaida doves (Zenaida aurita) on 12 territories with two learning tests in their natural habitat in Barbados. The dove pairs showed high site fidelity and territoriality, allowing us to test individuals repeatedly while accounting for the effects of territorial chases and pair bonds on our learning measures. We used a foraging apparat…
Color stimuli perception in presence of light scattering.
2006
Perception of different color contrast stimuli was studied in the presence of light scattering: in a fog chamber in Clermont-Ferrand and in laboratory conditions where light scattering of similar levels was obtained, using different light scattering eye occluders. Blue (shortest wavelength) light is scattered in fog to the greatest extent, causing deterioration of vision quality especially for the monochromatic blue stimuli. However, for the color stimuli presented on a white background, visual acuity in fog for blue Landolt-C optotypes was higher than for red and green optotypes on the white background. The luminance of color Landolt-C optotypes presented on a LCD screen was chosen corresp…
The goldfish--a colour-constant animal.
1996
A series of either thirteen or fifteen coloured test fields with hues from blue through grey to yellow were presented on a black background. Goldfish were trained on a bluish-grey test field by food reward. In the training situation, the setup with the coloured papers was illuminated with white light. In the test situation, the colour of the illumination was changed to blue or yellow. In both test illuminations the goldfish preferred the training field in the same way as under white illumination despite the fact that this test field stimulated the cone types very differently from the training situation. As test fields were present that excited the cones in exactly the same way as under whi…
Spatio-Chromatic Adaptation via Higher-Order Canonical Correlation Analysis of Natural Images
2014
Independent component and canonical correlation analysis are two general-purpose statistical methods with wide applicability. In neuroscience, independent component analysis of chromatic natural images explains the spatio-chromatic structure of primary cortical receptive fields in terms of properties of the visual environment. Canonical correlation analysis explains similarly chromatic adaptation to different illuminations. But, as we show in this paper, neither of the two methods generalizes well to explain both spatio-chromatic processing and adaptation at the same time. We propose a statistical method which combines the desirable properties of independent component and canonical correlat…
Simultaneous Color Contrast in Goldfish— a Quantitative Study
1997
AbstractA set of 9–15 colored test fields was presented to goldfish. In Experiment 1, test field hues ranged from green through yellow to red; in Experiment 2, the hues varied from blue through gray to yellow. In the training conditions, the test fields were presented with a gray or black surround. The fish learned to choose one intermediate test field hue by rewarding them with food. In the test conditions, the color of the surround was changed from gray to green, or red (Experiment 1), and from black to blue, or yellow (Experiment 2). The choice behavior of the goldfish changed substantially: one of the test fields other than the training test field was preferred. Direction and strength o…
Which Attribute of Ceiling Color Influences Perceived Room Height?
2018
Objective:We investigate effects of the hue, saturation, and luminance of ceiling color on the perceived height of interior spaces.Background:Previous studies have reported that the perceived height of an interior space is influenced by the luminance of the ceiling, but not by the luminance contrast between ceiling and walls: brighter ceilings appeared higher than darker ceilings, irrespective of wall and floor luminance. However, these studies used solely achromatic colors. We report an experiment in which we extend these findings to effects of chromatic ceiling colors.Methods:We presented stereoscopic room simulations on a head-mounted display (Oculus Rift DK2) and varied hue (red, green,…
Behavioural thresholds of blue tit colour vision and the effect of background chromatic complexity
2020
Vision is a vital attribute to foraging, navigation, mate selection and social signalling in animals, which often have a very different colour perception in comparison to humans. For understanding how animal colour perception works, vision models provide the smallest colour difference that animals of a given species are assumed to detect. To determine the just-noticeable-difference, or JND, vision models use Weber fractions that set discrimination thresholds of a stimulus compared to its background. However, although vision models are widely used, they rely on assumptions of Weber fractions since the exact fractions are unknown for most species. Here, we test; i) which Weber fractions in lo…
Nonlinearities and Adaptation of Color Vision from Sequential Principal Curves Analysis
2016
Mechanisms of human color vision are characterized by two phenomenological aspects: the system is nonlinear and adaptive to changing environments. Conventional attempts to derive these features from statistics use separate arguments for each aspect. The few statistical explanations that do consider both phenomena simultaneously follow parametric formulations based on empirical models. Therefore, it may be argued that the behavior does not come directly from the color statistics but from the convenient functional form adopted. In addition, many times the whole statistical analysis is based on simplified databases that disregard relevant physical effects in the input signal, as, for instance…