Motion parallax and absolute distance.

AbstractSince Kepler (1604) and Descartes (1638), ‘vergence’ (the angular rotation of the eyes) has been thought of as one of our most important absolute distance cues. But vergence has never been tested as an absolute distance cue divorced from obvious confounding cues such as binocular disparity. In this article we control for these confounding cues for the first time by gradually manipulating vergence, and find that observers fail to accurately judge distance from vergence. We consider a number of different interpretations of these results, and argue that the most principled response to these results is to question the general effectiveness of vergence as an absolute distance cue. Given other absolute distance cues (such as motion parallax and vertical disparities) are limited in application, this poses a real challenge to our contemporary understanding of visual scale.

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The Task-Dependent use of Binocular Disparity and Motion Parallax under Natural Viewing Conditions

Perception ◽

10.1068/v970186 ◽

1997 ◽

Vol 26 (1_suppl) ◽

pp. 99-99 ◽

Cited By ~ 1

Author(s):

M F Bradshaw ◽

B De Bruyn ◽

R A Eagle ◽

A D Parton

Keyword(s):

Binocular Disparity ◽

Motion Parallax ◽

Static Condition ◽

Matching Task ◽

Viewing Distance ◽

Horizontal Meridian ◽

Absolute Distance ◽

Physical Stimuli ◽

Additional Improvement ◽

Better Than

The use of binocular disparity and motion parallax information was compared in three different psychophysical tasks for which natural viewing and physical stimuli were used. Natural viewing may be an important factor in interpreting experiments which have addressed the ability to use disparity and parallax both separately and in combination (see Frisby et al, 1996 Perception25 129 – 154). The stimuli consisted of configurations of three bright LEDs carefully aligned in the horizontal meridian and presented in darkness. The distance of the middle LED (flashing at 5 Hz) could be adjusted along the midline in accordance with the tasks which included: (i) a depth nulling task, (ii) a depth matching task, and (iii) a shape task—match base/height of triangle. Each task was performed at two viewing distances (1.5 and 3.0 m) and under four different viewing conditions: (i) monocular-static, (ii) monocular-moving, (iii) binocular-static, and (iv) binocular-moving. Note that the different tasks differ in their dependence on viewing distance, and the available cues for viewing distance differ between viewing conditions. Four observers made ten settings in each condition at each distance. Observers, as expected, performed badly (bias and accuracy) in all tasks in the monocular-static condition. Nulling was accurate in the other viewing conditions (no estimate of viewing distance required). Performance was best in the matching task (ratio of viewing distances) but although binocular-static was significantly better than monocular-moving performance in this and in the shape task (absolute distance required), there was no additional improvement in the binocular-moving condition. Results show that observers can recover structure accurately from parallax or disparity information in real-world stimuli.

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Motion Parallax and Absolute Distance

10.21236/ad0742078 ◽

1971 ◽

Cited By ~ 1

Author(s):

Steven H. Ferris

Keyword(s):

Motion Parallax ◽

Absolute Distance

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Do We See Scale?

10.1101/371948 ◽

2018 ◽

Author(s):

Paul Linton

Keyword(s):

Visual System ◽

Motion Parallax ◽

Angular Size ◽

Absolute Distance ◽

Familiar Size ◽

Effective Distance ◽

Distance Information ◽

Vertical Disparity ◽

Three Stages ◽

The Cost

The visual system is supposed to extract distance information from the environment in order to scale the size and distance of objects in the visual scene. The purpose of this article is to challenge this account in three stages: First, I identify three shortcomings of the literature on vergence as our primary cue to near distances. Second, I present the results from two experiments that control for these shortcomings, but at the cost of eradicating vergence and accommodation as effective distance cues (average gain of y = 0.161x + 38.64). Third, I argue that if all our cues to distance are either (a) ineffective (vergence; accommodation; motion parallax), (b) merely relative (angular size; diplopia), or (c) merely cognitive (familiar size; vertical disparity), then the visual system does not appear to extract absolute distance information, and we should be open to the possibility that vision functions without scale.

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