Estimates of the frequency metameric surfaces, which appear same to eye under one illuminant but different another, were obtained from 50 hyperspectral images natural scenes. The degree metamerism was specified with respect a color-difference measure after allowing for full chromatic adaptation. relative pairs expressed as proportion all surfaces in scene, very low. Depending on criterion metamerism, it ranged about 10(-6) 10(-4) largest change tested, daylight correlated color temperature...

Quantitative measurements of perceptual colour constancy show that human observers have a limited and variable ability to match coloured surfaces in scenes illuminated by different light sources. Observers can, however, make fast reliable discriminations between changes illuminant the reflecting properties scenes, discriminative might be based on visual coding spatial relations. This could provided ratios cone-photoreceptor excitations produced from surfaces: for large class pigmented with...

For some sets of surfaces, the spatial ratios cone-photoreceptor excitations produced by light reflected from pairs surfaces are almost invariant under illuminant changes. These include large populations spectral reflectances, which represent individual natural but not their relative abundances in nature. The aim this study was to determine whether cone-excitation preserved changes within visual environment. A fast hyperspectral imaging system used obtain 640,000 reflectance spectra each 30...

In natural complex environments, the elevation of sun and presence occluding objects mutual reflections cause variations in spectral composition local illumination across time location. Unlike changes their consequences for color appearance constancy, spatial scenes have received relatively little attention. The aim present work was to characterize these by imaging. Hyperspectral radiance images were obtained from 30 rural urban which neutral probe spheres embedded. spectra at 17 sample...

If surfaces in a scene are to be distinguished by their color, neural representation at some level should ideally vary little with the color of illumination. Four possible codes were considered: von-Kries-scaled cone responses from single points scene, spatial ratios produced light reflected pairs points, and these quantities obtained sharpened (opponent-cone) responses. The effectiveness identifying was quantified information-theoretic measures. Data drawn sample 25 rural urban scenes...

The number of colors discernible by normal trichromats has been estimated for the idealized object-color solid. How well these estimates apply to natural scenes is an open question, as it unknown how much their approach theoretical limits. aim this work was estimate based on a database hyperspectral images 50 scenes. color volume each scene computed in CIELAB space and analyzed using CIEDE2000 color-difference formula. It found that set about 30% maximum full solid, corresponded 2.3 million...

In a previous study based on monitor simulations of artistic paintings, it was found that the average correlated color temperature (CCT) daylight preferred by large set observers to illuminate paintings around 5100 K. The goal present test if this result holds in real viewing conditions, i.e., with and light sources. same 11 were tested conditions illuminated spectrally tunable source accurate simulations. To ensure uniform illumination across only central part visible observers. It CCT for...

Abstract Many spectral‐recovery methods using RGB digital cameras assume the underlying smoothness of illuminant and reflectance spectra, apply low‐dimensional linear models. The aim present work was to test whether a direct‐mapping method could be used instead linear‐models approach recover spectral radiances reflectances from natural scenes with an camera colored filters. In computer simulations, conventional up three filters image drawn hyperspectral database. Three measures were evaluate...

The visual effects of lighting on art paintings is an important aspect that should be considered by museum curators. aim this work was to determine the correlated color temperature (CCT) daylight illumination preferred observers when appreciating paintings. Hyperspectral images 11 oil were collected at museum, and appearance under illuminants with CCT from 25,000 K 3600 computed. In a psychophysical experiment using precise CRT reproductions paintings, had adjust illuminant such it produced...

Painters reproduce some spatial statistical regularities of natural scenes. To what extent they replicate their color statistics is an open question. We investigated this question by analyzing the colors 50 scenes rural and urban environments 44 paintings with abstract figurative compositions. The analysis was carried out using hyperspectral imaging data from both sets focused on gamut distribution in CIELAB space. results showed that paintings, like scenes, have gamuts elongated shapes...

Ratios of excitations in each cone–photoreceptor class produced by light reflected from pairs surfaces a scene are almost invariant under natural illuminant changes. The stability these spatially defined ratios may explain the remarkable ability human observers to efficiently discriminate changes surface reflectances. Spatial cone–excitation not, however, exactly invariant. This study is concerned with observers' sensitivity invariance violations. Simulations Mondrian paintings either 49 or...

To what extent do observers' judgments of surface color with natural scenes depend on global image statistics? address this question, a psychophysical experiment was performed in which images under two successive daylights were presented computer-controlled high-resolution monitor. Observers reported whether there change reflectance test the scene. The obtained hyperspectral imaging system and included variously trees, shrubs, grasses, ferns, flowers, rocks, buildings. Discrimination...

The illumination in natural environments varies through the day. Stable inferences about surface color might be supported by spatial ratios of cone excitations from reflected light, but their invariance has been quantified only for global changes illuminant spectrum. aim here was to test under both spectrum and geometry, especially distribution shadows. Time-lapse hyperspectral radiance images were acquired five outdoor vegetated nonvegetated scenes. From each scene, 10,000 pairs points...

Color composition in paintings is a critical factor affecting observers' aesthetic judgments. We examined preferences for the color of Japanese and Occidental when their gamut was rotated. In experiment, observers were asked to select preferred image from original three hue-rotated images four-alternative forced choice paradigm. Despite being unfamiliar with presented artwork, (0 degrees) more frequently than ones. Furthermore, paintings' superiority observed divided into small square pieces...

Performance of multispectral devices in recovering spectral data has been intensively investigated some applications, as characterization art paintings, but received little attention the context natural illumination. This study quality estimation daylight-type illuminants using a commercial digital CCD camera and set broadband colored filters. Several recovery algorithms that did not need information about sensitivities sensors nor eigenvectors to describe spectra were tested. Tests carried...

Theoretical analyses of spectral reflectances natural surfaces suggest that their perceived colors can be well reproduced by approximations comprising combinations three or four basis functions. The aim the present work was to assess psychophysically number functions necessary reproduce entire outdoor scenes. Hyperspectral images 20 such scenes were each subjected a principal component analysis and then with variable quality color approximation under daylight illumination quantified...