Occlusion edge blur: a cue to relative visual depth

Abstract

We studied whether the blur/sharpness of an occlusion boundary between a sharply focused surface and a blurred surface is used as a relative depth cue. Observers judged relative depth in pairs of images that differed only in the blurriness of the common boundary between two adjoining texture regions, one blurred and one sharply focused. Two experiments were conducted; in both, observers consistently used the blur of the boundary as a cue to relative depth. However, the strength of the cue, relative to other cues, varied across observers. The occlusion edge blur cue can resolve the near/far ambiguity inherent in depth-from-focus computations.

Coarse Blobs or Fine Edges? Evidence That Information Diagnosticity Changes the Perception of Complex Visual Stimuli

“…Scale processing is a low-level task which has been shown to precede many early visual tasks such as motion (Morgan, 1992), stereopsis (Legge & Gu, 1989;Schor, Wood & Ogawa, 1984), depth perception (Marshall, Burbeck, Ariely, Rolland, & Martin, 1996) and saccade programming (Findlay, Brogan, & Wenban-Smith, 1993). Following the psychophysics of sinewave gratings, psychological and computational recognition research has often assumed that coarse blobs should be recognized before fine boundary edges in complex visual stimuli such as faces, objects, and scenes.…”

Blur Discrimination and its Relation to Blur-Mediated Depth Perception

“…This procedure is similar to that employed previously by Marshall et al (1996) but with the added benefit of allowing independent manipulation of the properties of the two image regions (different contrasts, luminances, etc).…”

“…Pentland (1987) identified image blur as a more general source of depth information both in machine vision and in human vision. However, only recently has blur-mediated depth perception become a matter for investigation in psychophysical studies (Marshall et al 1996;Mather 1996Mather , 1997O'Shea et al 1997;Mather and Smith 2000). Owing to the depth-of-focus limitations of the eye's optics, retinal images of objects nearer or farther than the plane of fixation are blurred by an amount that depends on their relative distance from the fixation plane.…”

“…This might lead one to assume that it is not possible to determine depth ordering on the basis of blur information alone. However,`border blur'öthe degree of blur at the border between blurred and unblurred regions in the image (Marshall et al 1996;Mather 1996)öoffers a possible means of determining depth order using only blur. If the border is blurred, it must be attached to the blurred region, and must therefore be the occluding edge of a nearer (blurred) object.…”

Diagnostic recognition: task constraints, object information, and their interactions

“…5). Such top-down influence of task constraints on scale perception is particularly interesting given the precedence the latter has on many processes of early vision such as stereopsis (Schor et al, 1984;Legge and Gu, 1989), motion (Morgan, 1992), depth perception (Marshall et al, 1996) and saccade programming (Findlay et al, 1993).…”