Cues to Viewing Distance for Stereoscopic Depth Constancy

There has long been a problem concerning the presence in the visual cortex of binocularly activated cells that are selective for vertical stimulus disparities because it is generally believed that only horizontal disparities contribute to stereoscopic depth perception. The accepted view is that stereoscopic depth estimates are only relative to the fixation point and that independent information from an extraretinal source is needed to scale for absolute or egocentric distance. Recently, however, theoretical computations have shown that egocentric distance can be estimated directly from vertical disparities without recourse to extraretinal sources. There has been little impetus to follow up these computations with experimental observations, because the vertical disparities that normally occur between the images in the two eyes have always been regarded as being too small to be of significance for visual perception and because experiments have consistently shown that our conscious appreciation of egocentric distance is rather crude and unreliable. Nevertheless, the veridicality of stereoscopic depth constancy indicates that accurate distance information is available to the visual system and that the information about egocentric distance and horizontal disparity are processed together so as to continually recalibrate the horizontal disparity values for different absolute distances. Computations show that the recalibration can be based directly on vertical disparities without the need for any intervening estimates of absolute distance. This may partly explain the relative crudity of our conscious appreciation of egocentric distance. From published data it has been possible to calculate the magnitude of the vertical disparities that the human visual system must be able to discriminate in order for depth constancy to have the observed level of veridicality. From published data on the induced effect it has also been possible to calculate the threshold values for the detection of vertical disparities by the visual system. These threshold values are smaller than those needed to provide for the recalibration of the horizontal disparities in the interests of veridical depth constancy. An outline is given of the known properties of the binocularly activated cells in the striate cortex that are able to discriminate and assess the vertical disparities. Experiments are proposed that should validate, or otherwise, the concepts put forward in this paper.

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Some consequences of stereoscopic depth constancy

Perception & Psychophysics ◽

10.3758/bf03199874 ◽

1979 ◽

Vol 26 (3) ◽

pp. 235-240 ◽

Cited By ~ 17

Author(s):

Hans Wallach ◽

Barbara Gillam ◽

Leonard Cardillo

Keyword(s):

Stereoscopic Depth ◽

Depth Constancy

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Stereoscopic depth constancy from a different direction

Vision Research ◽

10.1016/j.visres.2020.10.003 ◽

2021 ◽

Vol 178 ◽

pp. 70-78

Author(s):

Robert S. Allison ◽

Laurie M. Wilcox

Keyword(s):

Stereoscopic Depth ◽

Depth Constancy

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Adaptation in stereoscopic depth constancy

Perception & Psychophysics ◽

10.3758/bf03204458 ◽

1980 ◽

Vol 27 (5) ◽

pp. 403-408 ◽

Cited By ~ 2

Author(s):

Ann O’Leary ◽

Hans Wallach

Keyword(s):

Stereoscopic Depth ◽

Depth Constancy

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Failures of stereoscopic depth constancy: Fact or artefact?

Journal of Vision ◽

10.1167/6.6.271 ◽

2010 ◽

Vol 6 (6) ◽

pp. 271-271 ◽

Cited By ~ 1

Author(s):

B. J. Rogers

Keyword(s):

Stereoscopic Depth ◽

Depth Constancy

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The Interaction of Oculomotor Cues and Stimulus Size in Stereoscopic Depth Constancy

Perception ◽

10.1068/p200733 ◽

1991 ◽

Vol 20 (6) ◽

pp. 733-754 ◽

Cited By ~ 36

Author(s):

Thomas S Collett ◽

Urs Schwarz ◽

Erik C Sobel

Keyword(s):

Angular Size ◽

Natural World ◽

Angular Width ◽

Viewing Distance ◽

Image Size ◽

Planar Surfaces ◽

Wide Range ◽

Close Range ◽

Simulated Surface ◽

Depth Constancy

In the natural world, observers perceive an object to have a relatively fixed size and depth over a wide range of distances. Retinal image size and binocular disparity are to some extent scaled with distance to give observers a measure of size constancy. The angle of convergence of the two eyes and their accommodative states are one source of scaling information, but even at close range this must be supplemented by other cues. We have investigated how angular size and oculomotor state interact in the perception of size and depth at different distances. Computer-generated images of planar and stereoscopically simulated 3-D surfaces covered with an irregular blobby texture were viewed on a computer monitor. The monitor rested on a movable sled running on rails within a darkened tunnel. An observer looking into the tunnel could see nothing but the simulated surface so that oculomotor signals provided the major potential cues to the distance of the image. Observers estimated the height of the surface, their distance from it, or the stereoscopically simulated depth within it over viewing distances which ranged from 45 cm to 130 cm. The angular width of the images lay between 2 deg and 10 deg. Estimates of the magnitude of a constant simulated depth dropped with increasing viewing distance when surfaces were of constant angular size. But with surfaces of constant physical size, estimates were more nearly independent of viewing distance. At any one distance, depths appeared to be greater, the smaller the angular size of the image. With most observers, the influence of angular size on perceived depth grew with increasing viewing distance. These findings suggest that there are two components to scaling. One is independent of angular size and related to viewing distance. The second component is related to angular size, and the weighting accorded to it grows with viewing distance. Control experiments indicate that in the tunnel, oculomotor state provides the principal cue to viewing distance. Thus, the contribution of oculomotor signals to depth scaling is gradually supplanted by other cues as viewing distance grows. Binocular estimates of the heights and distances of planar surfaces of different sizes revealed that angular size and viewing distance interact in a similar way to determine perceived size and perceived distance.

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Stereoscopic depth constancy

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2015.0253 ◽

2016 ◽

Vol 371 (1697) ◽

pp. 20150253 ◽

Cited By ~ 5

Author(s):

Phillip Guan ◽

Martin S. Banks

Keyword(s):

Spatial Frequency ◽

Visual System ◽

Three Dimensional ◽

Differential Sensitivity ◽

Depth Interval ◽

Viewing Distance ◽

Vertical Disparity ◽

Depth Variation ◽

The World ◽

Depth Constancy

Depth constancy is the ability to perceive a fixed depth interval in the world as constant despite changes in viewing distance and the spatial scale of depth variation. It is well known that the spatial frequency of depth variation has a large effect on threshold. In the first experiment, we determined that the visual system compensates for this differential sensitivity when the change in disparity is suprathreshold, thereby attaining constancy similar to contrast constancy in the luminance domain. In a second experiment, we examined the ability to perceive constant depth when the spatial frequency and viewing distance both changed. To attain constancy in this situation, the visual system has to estimate distance. We investigated this ability when vergence, accommodation and vertical disparity are all presented accurately and therefore provided veridical information about viewing distance. We found that constancy is nearly complete across changes in viewing distance. Depth constancy is most complete when the scale of the depth relief is constant in the world rather than when it is constant in angular units at the retina. These results bear on the efficacy of algorithms for creating stereo content. This article is part of the themed issue ‘Vision in our three-dimensional world’.

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