Introduction

Cornsweet, Tom N.

doi:10.1016/b978-0-12-189750-5.50005-1

Cited by 94 publications

(124 citation statements)

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“…There are several well-established factors that support lightness constancy in the face of these challenges. On the one hand, lateral inhibition between retinal neurons filters out shallow intensity gradients, which are mostly caused by illumination effects (4,5). On the other hand, more complex factors also have an effect on lightness perception, such as object shape (6)(7)(8)(9) or the interpretation of transparent surfaces (10,11).…”

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confidence: 99%

Optimal sampling of visual information for lightness judgments

Toscani

Valsecchi

Gegenfurtner

2013

Proc. Natl. Acad. Sci. U.S.A.

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The variable resolution and limited processing capacity of the human visual system requires us to sample the world with eye movements and attentive processes. Here we show that where observers look can strongly modulate their reports of simple surface attributes, such as lightness. When observers matched the color of natural objects they based their judgments on the brightest parts of the objects; at the same time, they tended to fixate points with above-average luminance. When we forced participants to fixate a specific point on the object using a gaze-contingent display setup, the matched lightness was higher when observers fixated bright regions. This finding indicates a causal link between the luminance of the fixated region and the lightness match for the whole object. Simulations with rendered physical lighting show that higher values in an object's luminance distribution are particularly informative about reflectance. This sampling strategy is an efficient and simple heuristic for the visual system to achieve accurate and invariant judgments of lightness.lightness constancy | lightness perception | visual perception | attention J udging the lightness of visual stimuli has been studied for centuries, since the original investigations by Weber (1) and Fechner (2). The light reaching the eye is the product of the illumination and the reflectance of the object, and also depends on the scene geometry (3). However, only the proportion of reflected light is an invariant property of the object and thus of great importance for vision. There are several well-established factors that support lightness constancy in the face of these challenges. On the one hand, lateral inhibition between retinal neurons filters out shallow intensity gradients, which are mostly caused by illumination effects (4, 5). On the other hand, more complex factors also have an effect on lightness perception, such as object shape (6-9) or the interpretation of transparent surfaces (10, 11). However, eye movements have been almost completely neglected so far, even though a general influence of viewing behavior has been shown for some color constancy tasks (12)(13)(14)(15). This finding is surprising because the visual system needs to sample the local properties of objects and this is accomplished by moving the eyes and the focus of spatial attention around. Because visual acuity, luminance sensitivity, contrast sensitivity, and color sensitivity change with retinal eccentricity (16-18), our visual system has to stitch together its representation of the world from many small samples to analyze the visual scene in detail. Peripheral vision is not only characterized by poor resolution, but also the appearance of basic visual features-like spatial frequency, luminance, or chromatic saturation-is distorted in the periphery of the visual field (19-22). Eye movements may then be used to select relevant information, even for stimuli that are above threshold in peripheral vision. We investigated whether the distribution of fixations on an object has an e...

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confidence: 99%

Optimal sampling of visual information for lightness judgments

Toscani

Valsecchi

Gegenfurtner

2013

Proc. Natl. Acad. Sci. U.S.A.

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“…[8] VL represents the ratio of the actual contrast of a task to its threshold (50% detection) contrast. so it can be considered a normalized contrast.…”

Section: Other Modelsmentioning

confidence: 99%

Analysis of a Visual Performance Experiment

Clear

Berman

1984

Journal of the Illuminating Engineering Society

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“…Since it is assumed the process u(') is Gaussian , the results ~o tain e -i in equation (11)(12) are the same as the conditional 'naxim um l ike li ri o o~ e s 'imates of e and 2 [ 42].…”

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confidence: 99%

“…Fi gures : 1-1 2 ~n j 11-13 'or o-otb n oj e l s aes c ribed by equations (11)(12)(13)(14) and (11)(12)(13)(14)(15) . T -e absoL~t~ ~i " ere"ce Pit t Jre between the original and regenerated im ai e wi s ils o --'e: as wel l as the root mean square (rms) error.…”

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confidence: 99%