Pictorial Depiction and Perception

Depicting Objects

An important difference between perceiving an object in a scene and in a picture is that a person can move around in a scene to view the object from different angles, but in a picture the object is frozen. The viewer sees the object from the point of view selected by the artist and cannot inspect it further. The ability to view objects in scenes from different angles is important, because although many objects—especially familiar ones—appear just as one would expect them to when viewed from different angles, surprises can potentially occur. Consider, for example the metal horse in Figure 1, which appears to be a “realistic” horse from viewpoint 1 (Figure 1a), but which is revealed to be distorted when observed from viewpoints 2 and 3 (Figures 1b and c). The fact that a single view of an object provides incomplete information about an object means that when a person views objects, he or she routinely makes assumptions about the objects. When the object is in the environment, the person can check these assumptions by moving to different viewpoints, but when the [Page 820]object is in a picture, there is no way of checking one's assumptions.

Figure 1 Three Views of a “Horse”

Note: Moving around an object can reveal its true shape.

Given that the information depicted in pictures is incomplete and can't be checked by changing the point of view, it is important that the artist depict individual objects as clearly as possible. One way to achieve this is to depict the object from a viewpoint that shows properties that are present at many viewing angles. For example, all three parallel edges of the book in Figure 2 are visible in the views shown in Figures 2(a) and (b). This property—three parallel edges—is called an invariant property of the book, because it is generally unaffected by variations in viewpoint. In contrast, the view in Figure 2(c) reveals an accidental property of the book, in which the three parallel edges are not visible. This situation occurs only on the rare occasions when the book is viewed so only one face is visible. Objects are difficult to identify when only accidental properties are visible, so it is important that artists avoid these viewpoints when depicting objects.

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