Brightness Model for Neutral Self-Luminous Stimuli and Backgrounds

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Image color appearance models (Image CAMs) have been developed to predict the perception of complex scenes and are mainly used for image rendering and video reproduction applications. Among these Image CAMs, iCAM is an Image CAM that takes an image as the input and provides the perceptual attributes for each pixel. On the other hand, nonimaging CAMs are widely used and validated, but they always assume a simple test scene of a uniform flat stimulus, a quasi‐neutral background, and a surround. This study presents an evaluation of the performance of iCAM when applied to these simple self‐luminous scenes in predicting the influence of background luminance, background size, saturation, and stimulus size on stimulus brightness. The results show that iCAM is capable of predicting the effect of background luminance and some background size scenarios. However, for unrelated self‐luminous stimuli (dark background), the model predictions do not match the reference data. An evaluation of the effect of the filter kernel size and its relation to the physiological mechanism of image processing inside the visual system has been investigated. Furthermore, the impact of saturation and stimulus size on brightness seems to be underestimated by the model, because the Helmholtz‐Kohlrausch and stimulus size effects are not included. Hence, these findings call for an enhanced Image CAM.

Section: Evaluation Of Icam Performancesupporting

confidence: 53%

Section: Evaluation Of Icam Performancementioning

confidence: 64%

Section: Evaluation Of Icam Performancementioning

confidence: 99%

Section: Brightness Prediction Of Neutral Stimuli and Neutral Backgmentioning

confidence: 99%

Section: Brightness Prediction Of Neutral Stimuli and Neutral Backgmentioning

confidence: 99%

See 3 more Smart Citations

Assessing the application of an image color appearance model to basic self‐luminous scenes

Phung

Leloup

Smet

et al. 2019

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Relationship between pupillary size, brightness, and photoreceptor responses for unrelated self‐luminous stimuli at low photopic light levels

Salinas¹,

Hermans

Sandoval³

et al. 2020

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Research on the correlation between the initial pupillary light reflex, the perceptual brightness, and the excitations of the photoreceptors was performed for unrelated self-luminous 10 stimuli at low photopic light levels (5 to 80 cd/ m 2). All stimuli were optically characterized using a spectroradiometer. For determining the pupillary diameter, an Eye Tracker was used. The perceived brightness was evaluated with the magnitude estimation method. Test stimuli were presented alternating with a reference stimulus and the Michelson contrast of the pupillary diameter between test and reference conditions was calculated. Six observers (three female and three male) participated, with ages between 30 and 39 years (with an average of 34.5 years). It was found that the coefficient of determination between the pupillary response and the perceived stimulus brightness was higher than the corresponding value for luminance, allowing the suggestion that brightness has a greater effect on pupillary size than luminance. Nevertheless, this is not the complete story: highly saturated red and blue stimuli both induce a high brightness perception but the pupil contraction induced by the blue stimuli is much greater than for the red stimuli. Pupillary diameter was also studied as a function of the relative excitations of the five photoreceptors. The effect of rod and ipRGC excitations on pupillary size variation seems to be larger than that of the other photoreceptors. However, for the working conditions prevailing in this research, it could be expected that rods are not very active and that the ipRGC response might be the major driving mechanism.

Brightness appearance of self‐luminous stimuli on a non‐uniform background

Phung

Kong

Leloup

et al. 2022

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Color appearance models (CAM) generate a set of visual correlates attributed to a stimulus such as hue, brightness, and saturation. However, most of their applicability is limited to stimuli perceived on a uniform background. Additionally, when focusing on brightness, multiple studies have been performed to model the mechanisms of brightness perception of a stimulus on a non‐uniform background. In this paper, experimental data are gathered and the insights of both approaches are combined. The influence of adding a neutral ring‐shaped luminous area in the background of a neutral circular stimulus has been investigated via a series of psychophysics experiments. The ring is presented at three luminance levels (90, 335, 1200 cd/m2) with three thicknesses (0.33, 0.67, and 1.00 cm) at four angular distances to the edge of the stimulus (1.2°, 6.4°, 11.3° and 16.1°). It is observed that when the ring is closer to the stimulus, the brightness inhibition becomes larger; obviously, the impact is also related to the ring's area and luminance. Inspired by the classical CAM, the cone excitations corresponding to the stimulus and the background are inserted in a compression‐adaptation formula to obtain a cone response proportional to the perceived brightness. The semi‐saturation constant occurring in this formula is modelled as a function of the cone excitation, the distance and the width of the ring. The results are overall promising, yet the model shows some shortcomings and more complex weighting functions might be needed. In the future, image‐based approaches should get more attention.