Cues to Viewing Distance for Stereoscopic Depth Constancy

Abstract

A veridical estimate of viewing distance is required in order to determine the metric structure of objects from binocular stereopsis. One example of a judgment of metric structure, which we used in our experiment, is the apparently circular cylinder task (E B Johnston, 1991 Vision Research 31 1351-1360). Most studies report underconstancy in this task when the stimulus is defined purely by binocular disparities. We examined the effect of two factors on performance: (i) the richness of the cues to viewing distance (using either a naturalistic setting with many cues to viewing distance or a condition in which the room and the monitors were obscured from view), and (ii) the range of stimulus disparities (cylinder depths) presented during an experimental run. We tested both experienced subjects (who had performed the task many times before under full-cue conditions) and naïve subjects. Depth constancy was reduced for the naïve subjects (from 62% to 46%) when the position of the monitors was obscured. Under similar conditions, the experienced subjects showed no reduction in constancy. In a second experiment, using a forced-choice method of constant stimuli, we found that depth constancy was reduced from 64% to 23% in naïve subjects and from 77% to 55% in experienced subjects when the same set of images was presented at all viewing distances rather than using a set of stimulus disparities proportional to the correct setting. One possible explanation of these results is that, under reduced-cue conditions, the range of disparities presented is used by the visual system as a cue to viewing distance.

Relative distance cues contribute to scaling depth from motion parallax

“…Our conclusion that relative distance cues affect absolute distance information is consistent with studies showing that estimations of perceived distance under reduced-cue conditions differ from those under full-cue conditions (Glennerster, Rogers, & Bradshaw, 1998;Sedgwick, 1986). Under reduced-cue conditions, an isolated object is typically viewed in total darkness, and the main cues about the object's distance are the absolute distance cues of accommodation and/or vergence (Glennerster et al, 1998;Gogel, 1972).…”

“…Under reduced-cue conditions, an isolated object is typically viewed in total darkness, and the main cues about the object's distance are the absolute distance cues of accommodation and/or vergence (Glennerster et al, 1998;Gogel, 1972). Under full-cue conditions, objects are typically viewed in an illuminated and structured environment, and, compared with reducedcue conditions,these conditions mainly add visual sources of information about the viewing environment such as relative distance cues (Gogel, 1972;.…”

Stereoscopic acuity and observation distance

“…The distance cues in the stimulus (e.g. Predebon, 1993;Glennerster et al, 1998) and the task the observer is required to do . Related results in physiology have been reported by Trotter et al (1992) who showed that some cells in area V1 of the monkey modulate their response with changes in viewing distance which suggests that retinal disparity alone may not determine the response characteristics of all the cells underlying disparity processing in the early visual pathway (see also Judge and Cumming, 1986;Erkelens, 2001).…”

Detecting binocular 3D motion in static 3D noise: no effect of viewing distance

“…There is evidence from a 3-D shape perception study that, in a restricted situation where only binocular disparity, accommodation and vergence information was present, the visual system makes shape discrimination errors consistent with mis-estimating viewing distance (Johnston, 1991). Other studies, in which vertical disparity and other information is present (for example see Rogers and Bradshaw, 1993;Glennerster et al, 1998), suggest that in a richer environment, viewing distance can sometimes be obtained veridically. It is likely that in the real world there would be sufficient visual information available to obtain an estimate of object distance, and thus to convert motion estimates from retinal to real-world coordinates.…”