scholarly journals Luminosity thresholds of colored surfaces are determined by their heuristic upper-limit luminances in the visual system

2021 ◽  
Author(s):  
Takuma Morimoto ◽  
Ai Numata ◽  
Kazuho Fukuda ◽  
Keiji Uchikawa
Keyword(s):  
Visual System ◽  
Luminance Level ◽  
Natural Environments ◽  
Test Field ◽  
Maximum Luminance ◽  
Color Distribution ◽  
Upper Limit ◽  
Circular Test ◽  
Real Objects ◽  
Upper Boundary

Some objects in the real world themselves emit a light, and we typically have a fairly good idea as to whether a given object is self-luminous or illuminated by a light source. However, it is not well understood how our visual system makes this judgement. This study aimed to identify determinants of luminosity threshold, a luminance level at which the surface begins to appear self-luminous. We specifically tested a hypothesis that our visual system knows a maximum luminance level that a surface can reach under the physical constraint that surface cannot reflect more lights that incident lights and apply this prior to determine the luminosity thresholds. Observers were presented a 2-degree circular test field surrounded by numerous overlapping color circles, and luminosity thresholds were measured as a function of (i) the chromaticity of the test field, (ii) the shape of surrounding color distribution and (iii) the color of illuminant lighting surrounding colors. We found that the luminosity thresholds strongly depended on test chromaticity and peaked around the chromaticity of test illuminants and decreased as the purity of the test chromaticity increased. However, the locus of luminosity thresholds over chromaticities were nearly invariant regardless of the shape of surrounding color distribution and generally well resembled the locus drawn from theoretical upper-limit luminance but also the locus drawn from the upper boundary of real objects. These trends were particularly evident for test illuminants on blue-yellow axis and curiously did not hold under atypical illuminants such as magenta or green. Based on these results, we propose a theory that our visual system empirically internalizes the gamut of surface colors under illuminants typically found in natural environments and a given surface appears self-luminous when its luminance exceeds this heuristic upper-limit luminance.

scholarly journals Color constancy based on the geometry of color distribution

2020 ◽  
Author(s):  
Takuma Morimoto ◽  
Takahiro Kusuyama ◽  
Kazuho Fukuda ◽  
Keiji Uchikawa
Keyword(s):  
Visual System ◽  
Computational Modeling ◽  
Color Constancy ◽  
Test Field ◽  
Color Gamut ◽  
Surface Color ◽  
Color Distribution ◽  
Proposed Model ◽  
Specific Shape

AbstractA white surface appears white under different lighting environments. This ability is referred to color constancy. The physical inputs to our visual system are dictated by the interplay between lights and surfaces, and thus for the surface color to be stably perceived, the illuminant influence needs to be discounted. To reveal our strategy to infer the illuminant color, we conducted three psychophysical experiments designed to test optimal color hypothesis: we internalize the physical color gamut under a particular illuminant and apply the prior to estimate the illuminant color. In each experiment, we presented 61 hexagons arranged without spatial gaps, where the surrounding 60 hexagons were set to have a specific shape in their color distribution. We asked participants to adjust the color of a center test field so that it appears a full-white surface placed under a test illuminant. Results and computational modeling suggested that although our proposed model is limited in accounting for estimation of illuminant intensity by human observers, it agrees fairly well with the estimates of illuminant chromaticity in most tested conditions. The accuracy of estimation generally outperformed other tested conventional color constancy models. These results support the hypothesis that our visual system can utilize the geometry of scene color distribution to achieve color constancy.

scholarly journals Luminosity thresholds of colored surfaces are determined by their upper-limit luminances empirically internalized in the visual system

2021 ◽  
Vol 21 (13) ◽  
pp. 3
Author(s):  
Takuma Morimoto ◽  
Ai Numata ◽  
Kazuho Fukuda ◽  
Keiji Uchikawa
Keyword(s):  
Visual System ◽  
Upper Limit

scholarly journals Color Harmonization, Deharmonization and Balancing in Augmented Reality

2021 ◽  
Vol 11 (9) ◽  
pp. 3915
Author(s):  
Emanuele Marino ◽  
Fabio Bruno ◽  
Fotis Liarokapis
Keyword(s):  
Augmented Reality ◽  
Crucial Importance ◽  
Color Distribution ◽  
The Real ◽  
Virtual Objects ◽  
The Third ◽  
Covered Area ◽  
Real Objects ◽  
Good Visibility

Color schemes play a crucial role in blending virtual objects with the real environment. Good color schemes improve user’s perception, which is of crucial importance for augmented reality. In this paper, we propose a set of novel methods based on the color harmonization methodology to recolor augmented reality content according to the real background. Three different strategies are proposed—harmonic, disharmonic, and balance—that allow for satisfying different needs in different settings depending on the application field. The first approach aims to harmonize the colors of virtual objects to make them consistent with the colors of the real background and reach a more pleasing effect to a human eye. The second approach, instead, can be adopted to generate a set of disharmonious colors with respect to real ones to be associated with the augmented virtual content to improve its distinctiveness from the real background. The third approach balances these goals by achieving a compromise between harmony and good visibility among virtual and real objects. Furthermore, the proposed re-coloring method is applied to three different case studies by adopting the three strategies to meet three different objectives, which are specific for each case study. Several parameters are calculated for each test, such as the covered area, the color distribution, and the set of generated colors. Results confirm the great potential of the proposed approaches to improve the AR visualization in different scenarios.

scholarly journals Natural image statistics at depth edges modulate perceptual stability

2020 ◽  
Author(s):  
Zeynep Başgöze ◽  
David N. White ◽  
Johannes Burge ◽  
Emily A. Cooper
Keyword(s):  
Visual System ◽  
Three Dimensional ◽  
Natural Image ◽  
Natural Scenes ◽  
Natural Environments ◽  
Large Set ◽  
Natural Image Statistics ◽  
Binocular Fusion ◽  
Perceptual Stability ◽  
Statistical Regularities

AbstractBinocular fusion relies on matching points in the two eyes that correspond to the same physical feature in the world. However, not all world features are binocularly visible. In particular, at depth edges parts of a scene are often visible to only one eye (so-called half occlusions). Accurate detection of these monocularly visible regions is likely to be important for stable visual perception. If monocular regions are not detected as such, the visual system may attempt to binocularly fuse non-corresponding points, which can result in unstable percepts. We investigated the hypothesis that the visual system capitalizes upon statistical regularities associated with depth edges in natural scenes to aid binocular fusion and facilitate perceptual stability. By sampling from a large set of stereoscopic natural image patches, we found evidence that monocularly visible regions near depth edges in natural scenes tend to have features more visually similar to the adjacent binocularly visible background region than to the adjacent binocularly visible foreground. The generality of these results was supported by a parametric study of three-dimensional (3D) viewing geometry in simulated environments. In two perceptual experiments, we examined if this statistical regularity may be leveraged by the visual system. The results show that perception tended to be more stable when the visual properties of the depth edge were statistically more likely. Exploiting regularities in natural environments may allow the visual system to facilitate fusion and perceptual stability of natural scenes when both binocular and monocular regions are visible.PrecisWe report an analysis of natural scenes and two perceptual studies aimed at understanding how the visual statistics of depth edges impact perceptual stability. Our results suggest that the visual system exploits natural scene regularities to aid binocular fusion and facilitate perceptual stability.

Preliminary Result on the Direct Assessment of Perceptible Simultaneous Luminance Dynamic Range

2021 ◽  
Author(s):  
Fu Jiang ◽  
Mark D. Fairchild
Keyword(s):  
Visual System ◽  
Dynamic Range ◽  
Luminance Level ◽  
Psychophysical Experiment ◽  
Range Data ◽  
Stimulus Luminance ◽  
Wide Dynamic Range ◽  
A Value ◽  
Log Linear ◽  
Full Adaptation

The human visual system is capable of adapting across a very wide dynamic range of luminance levels; values up to 14 log units have been reported. However, when the bright and dark areas of a scene are presented simultaneously to an observer, the bright stimulus produces significant glare in the visual system and prevents full adaptation to the dark areas, impairing the visual capability to discriminate details in the dark areas and limiting simultaneous dynamic range. Therefore, this simultaneous dynamic range will be much smaller, due to such impairment, than the successive dynamic range measurement across various levels of steady-state adaptation. Previous indirect derivations of simultaneous dynamic range have suggested between 2 and 3.5 log units. Most recently, Kunkel and Reinhard reported a value of 3.7 log units as an estimation of simultaneous dynamic range, but it was not measured directly. In this study, simultaneous dynamic range was measured directly through a psychophysical experiment. It was found that the simultaneous dynamic range is a bright-stimulus-luminance dependent value. A maximum simultaneous dynamic range was found to be approximately 3.3 log units. Based on the experimental data, a descriptive log-linear model and a nonlinear model were proposed to predict the simultaneous dynamic range as a function of stimulus size with bright-stimulus luminance-level dependent parameters. Furthermore, the effect of spatial frequency in the adapting pattern on the simultaneous dynamic range was explored. A log parabola function, representing a traditional Contrast Sensitivity Function (CSF), fitted the simultaneous dynamic range data well.

S-cone discrimination for stimuli with spatial and temporal chromatic contrast

2008 ◽  
Vol 25 (3) ◽  
pp. 349-354 ◽  
Author(s):  
DINGCAI CAO ◽  
ANDREW J. ZELE ◽  
VIVIANNE C. SMITH ◽  
JOEL POKORNY
Keyword(s):  
Visual System ◽  
Natural Environment ◽  
Stimulus Condition ◽  
Spatial And Temporal Variation ◽  
Natural Scenes ◽  
Test Field ◽  
Temporal Contrast ◽  
Chromatic Contrast ◽  
Laboratory Methods ◽  
Spatio Temporal

In the natural environment, color discriminations are made within a rich context of spatial and temporal variation. In classical laboratory methods for studying chromatic discrimination, there is typically a border between the test and adapting fields that introduces a spatial chromatic contrast signal. Typically, the roles of spatial and temporal contrast on chromatic discrimination are not assessed in the laboratory approach. In this study, S-cone discrimination was measured using stimulus paradigms that controlled the level of spatio-temporal S-cone contrast between the tests and adapting fields. The results indicate that S-cone discrimination of chromaticity differences between a pedestal and adapting surround is equivalent for stimuli containing spatial, temporal or spatial-and-temporal chromatic contrast between the test field and the surround. For a stimulus condition that did not contain spatial or temporal contrast, the visual system adapted to the pedestal instead of the surround. The data are interpreted in terms of a model consistent with primate koniocellular pathway physiology. The paradigms provide an approach for studying the effects of spatial and temporal contrast on discrimination in natural scenes.

Color and Luminance

2017 ◽  
Author(s):  
Stuart Anstis
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Test Field

Color and luminance interact in many ways in the human visual system. For instance, the colors in an afterimage, which are due to adaptation of retinal cones, are especially vivid when test contours, presented after the adapting image, coincide with the blurred edges of the afterimage. A single colored adapting pattern can give rise to two differently colored afterimages, according to the position of black lines in the test field. This shows that colors seen by the low-acuity chromatic pathways will diffuse outward along, but not across, luminance contours. This is also true for real colors. Finally, flicker-augmented contrast shows that the visual system, when given a choice, will select the most salient color/luminance borders in a stimulus.

scholarly journals COLORBLIND VISION

1947 ◽  
Vol 31 (2) ◽  
pp. 141-152 ◽  
Author(s):  
Selig Hecht ◽  
Yun Hsia
Keyword(s):  
Color Vision ◽  
Total Loss ◽  
Test Field ◽  
Receptor System ◽  
System A ◽  
Normal Color Vision ◽  
Circular Test

1. Measurements have been made of the dark-adapted foveal threshold of normal and colorblind persons in five parts of the spectrum using a 1° circular test field. 2. Compared to normals, protanopes (red-blinds) show an elevation of the threshold which increases slowly from blue to yellow and rises rapidly thereafter until in the red the threshold is more than ten times as high as normal. Deuteranopes (green-blinds) do not show so high an elevation, their maximum in the green being only about 70 per cent above normal. 3. These threshold elevations correspond to luminosity losses in the spectrum. For the protanope the total loss in the spectrum is nearly one-half of the normal luminosity; for the deuteranope it is nearly two-fifths of normal. 4. Such losses support the idea that colorblindness corresponds to the loss of one of the three receptor systems usually postulated to account for normal color vision. However, the color sensations reported by colorblind persons, especially monocular colorblinds, do not support the idea of a lost or inactivated receptor system. A fresh explanation for colorblindness is called for to reconcile these conflicting kinds of evidence.

SEEMORE: Combining Color, Shape, and Texture Histogramming in a Neurally Inspired Approach to Visual Object Recognition

1997 ◽  
Vol 9 (4) ◽  
pp. 777-804 ◽  
Author(s):  
Bartlett W. Mel
Keyword(s):  
Object Recognition ◽  
Visual System ◽  
Three Dimensional ◽  
Feature Space ◽  
Image Plane ◽  
Classification Performance ◽  
Visual Object ◽  
Visual Object Recognition ◽  
Real Objects ◽  
Dimensional Object

Severe architectural and timing constraints within the primate visual system support the conjecture that the early phase of object recognition in the brain is based on a feedforward feature-extraction hierarchy. To assess the plausibility of this conjecture in an engineering context, a difficult three-dimensional object recognition domain was developed to challenge a pure feedforward, receptive-field based recognition model called SEEMORE. SEEMORE is based on 102 viewpoint-invariant nonlinear filters that as a group are sensitive to contour, texture, and color cues. The visual domain consists of 100 real objects of many different types, including rigid (shovel), nonrigid (telephone cord), and statistical (maple leaf cluster) objects and photographs of complex scenes. Objects were in dividually presented in color video images under normal room lighting conditions. Based on 12 to 36 training views, SEEMORE was required to recognize unnormalized test views of objects that could vary in position, orientation in the image plane and in depth, and scale (factor of 2); for non rigid objects, recognition was also tested under gross shape deformations. Correct classification performance on a test set consisting of 600 novel object views was 97 percent (chance was 1 percent) and was comparable for the subset of 15 nonrigid objects. Performance was also measured under a variety of image degradation conditions, including partial occlusion, limited clutter, color shift, and additive noise. Generalization behavior and classification errors illustrate the emergence of several striking natural shape categories that are not explicitly encoded in the dimensions of the feature space. It is concluded that in the light of the vast hardware resources available in the ventral stream of the primate visual system relative to those exercised here, the appealingly simple feature-space conjecture remains worthy of serious consideration as a neurobiological model.

scholarly journals Distribution of lichen thalli Pseudevernia furfuracea (L.) Zopf along Pinus sylvestris trunk in different types of pine forests with different relief positions

2020 ◽  
Vol 9 (3) ◽  
pp. 137-141
Author(s):  
Yulia G. Suetina
Keyword(s):  
Population Density ◽  
Pinus Sylvestris ◽  
National Park ◽  
Lower Boundary ◽  
Pine Forest ◽  
Pine Forests ◽  
Pseudevernia Furfuracea ◽  
Upper Limit ◽  
Different Types ◽  
Upper Boundary

The research of the Pseudevernia furfuracea population was carried out in the Mari El Republic on the territory of the Mari Chodra National Park. The lichen-mossy and cowberry pine forests were studied with different relief positions: uplands and lowlands. The paper discusses the use of two indicators of population density: D₁ is a number of thalli on the tree; D₂ is a number of thalli in the substrate area. The distribution of thalli along the trunk of Pinus sylvestris depends on the characteristics of the stand, characteristics of the tree and the position of the trees in the relief. In a well-lightened lichen-mossy pine forest the distribution of the number of thallus is equal at different exposures, but it is different due to the heights of the trunk. The maximum number of thalli is typical for a height of 0,51 m. The most number of thallus grows at the southern and western expositions in less lightened cowberry pine forests. There is a shift in the height of the number of thallus to a height of 11,5 m. There is a dependence of the upper boundary of the thallus distribution along the trunk on the height of the lamellar bark. The highest upper limit of thallus growth (a height of 4,8 m) is typical for the lowering of the lichen-mossy pine forest, where the lamellar bark rises to a height of 7,2 m. The lower boundary of the thallus settlement depends on microclimatic factors. Among them the decisive factor is light. The smallest lower boundary of a thallus settlement (a height of 0,2 m) is typical for an elevation in a lichen-mossy pine forest. This habitat has the highest population density of P. furfuracea.

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