Compression of visual space in natural scenes and in their photographic counterparts

Abstract

Classical theories of space perception posit continuous distortions of subjective space. These stand in contrast to the quantitatively and qualitatively different distortions experienced in space that is represented pictorially. Wechallenge several aspects of these theories. Comparing real-world objects with depictions of the same objects, we investigated to what extent distortions are introduced by the photographic medium. Comers of irregularly shaped buildings had to be judged in terms of the vertical dihedral angles subtended by two adjacent walls. Across all conditions, a robust effect of viewing distance was found: Buildingcomers appear to flatten out with distance. Moreover,depictions of comers produce remarkably similar results and should not receive a different theoretical treatment than do real-world scenes. The flattening of vertical angles cannot be explained by a linear distortion of the entire visual space. We suggest that, for natural scenes, compression of space is local and dependent on contextual information. Visually perceived depth in spatial arrangements has been studied within the context of two rather distinct frameworks. First, many theories of subjective space are based on the notion that perceived space is distorted in a uniform fashion and that a specific transformation can be found that describes the mapping relations between the Euclidean space of the world and our subjective space. Second, theories of spatial representation are concerned with distortions that arise in the process of representing space-mainly, the effects caused by pictorial rendition, such as projective distortions or the apparent flattening of the scene. In this study, we attempt to establish a relationship between the two frameworks by comparing judgments made in real scenes with judgments based on photographic renditions ofthe same scenes. Surprisingly, we found distortions to be very similar. We had observers judge the dihedral angles of building comers from a va-H

Distance estimation in vista space

“…Likewise, in a more anecdotal fashion, Baden-Powell (1944) suggested that merely looking uphill or downhill leads to underestimation of distance. Sagittal compression in action space is also consistent with the finding that right angles of buildings are perceptually flattened in action space (Hecht et al, 1999). If these findings are taken together, the case for compression is fairly strong for action space, whereas it is anything but clear for vista space.…”

The impact of spatiotemporal sampling on time-to-contact judgments

“…Typically, significant sagittal compression effects are found, resulting in large distances being grossly underestimated (Loomis, Da Silva, Philbeck, & Fukusima, 1996). These effects persist in pic-tures as well as in real-world viewing (Hecht, van Doorn, & Koenderink, 1999). Such spatial compression suggests that arrival times may be underestimated for objects that move in depth away from or toward the observer.…”

Voluntarily controlled bi–stable slant perception of real and photographed surfaces

“…van Doorn et al 2001) or scenes (Hecht et al 1999). We are specifically interested in perceived slant.…”