In four experiments, we explored the perception of facial distortions seen in pictures viewed from the side or from above or below. In all four, however, we disguised the slant of the picture surface by using a double-projection technique that removed binocular and monocular cues: Faces were digitized, distorted to mimic a particular slant behind the image plane, cropped to a frame, and presented to viewers for their judgments. In the first experiment, we found that simulated rotations around a horizontal axis (pictures seen as if from above or below) created more noticeable distortions in faces than did simulated rotations around a vertical axis (pictures seen as if from the left or right). In the second experiment, pursuing a result from the first but with a between-subjects design, we found that pictured faces with a slant around a vertical axis of 22°w ere seen as having no more distortion than unslanted faces. In the third experiment, we placed each image within a frame slanted either in the same way as or differently from the picture, and found no effect of frame. In the fourth experiment, we determined that viewers had little ability to match appropriately slanted frames with slanted pictures. Thus, we claim that part of the reason why one can look at moderately slanted pictures without perceptual interference is that the distortions in the image are subthreshold, or perhaps within the bounds of acceptability. These results contrast with the generally accepted theory that viewers mentally compensate for distortions in moderately slanted pictures. Perhaps the most commonplace, but theoretically most surprising, aspect of the perception of realistic pictures, photographs, and cinema is their viewpoint-independent utility. That is, a viewer need not be directly in front of a picture or movie at the point from which it was composed (or shot) to enjoy it, to understand it, to admire it, or simply to look at it and make sense of what is seen. Viewpoint-independent utility is theoretically surprising because the geometric layout of virtual space "behind" the picture surface is correct only for one viewpoint, variously called the station point (Bengston, Stergios, Ward, & Jester, 1980; Cutting, 1986a; Gibson, 1979; Haber, 1978), the center of projection (Farber & Rosinski, 1978; Kubovy, 1986), or the composition point (Cutting, 1988). (The line to this point from the center of the picture is called the principal ray, to which we will refer later.) Only by looking at a picture from the composition point is a cross section of the original, monocular optical array faithfully recreated. All other viewpoints induce optical deformations of greater or lesser extent. The issue at stake in this paper is how much slant-induced distortion produces a noticeable difference. Although Leonardo (Richter, 1883 /1970 ) and other 16th-century artists were concerned with particular deformations in pictures, it was La Gournerie (1859; see also This research was supported by National Science Foundation Grant BNS-8818971. Correspondence should be sent to J E. Cutting, Department of Psychology, Uris Hall, Cornell Umvers~ty, Ithaca, NY 14853-7601 We thank David Dunning for allowing us to gather the data of Experiment 2 ~n his class T A. Busey ~s now in the Department of Psychology at the Umversity of Washington, Seattle, WA 98195. Kubovy, 1986; Pirenne, 1970) who performed the first systematic global analysis of virtual space in pictures. He noted that when one's eye is not at the composition point, the virtual space behind the picture surface changes. When one is closer to a photograph, for example, than the focal length of the lens times the magnification, apparent depth should be compressed; when one is farther away, it should expand; and, most interestingly, when one is off to one side, it should undergo affine shear.
Reinforcing this idea, the fourth experiment of REF showed the frame to play little role in the perception of distortion.
Compensation is unnecessary for the perception of faces in slanted pictures
Perception & psychophysics
Perception & psychophysics
Psychology Medicine