Journal of the Society of Motion Picture and Television Engineers (1950-1954)

that these forms see all aspects of space from a truly egocentric point of reference. Each eye perceives the objects in space in panoramic fashion and in depth. The primitive and basic responses to light perception are still present in man's peripheral field and represent the more archaic panoramic vision. In the evolution of vertebrates up to man the eyes have migrated anteriorly so that portions of the originally monocular fields overlap. The area of the overlap gives us single binocular vision with an added advantage which is absent in panoramic vision. However, the original panoramic field has been reduced in size; in man it is 200° at the most. It would appear that in panoramic vision the visual perception of space was originally bidimensional and restricted to the localization on objects in a flat visual field. It is an erroneous assumption that any form (fish, frog or oneeyed person) with panoramic vision sees the surrounding world as flat, like a photograph; and that judgment of distances is totally faulty. Fish open their mouths at precisely the right time to seize their prey. The Gecko lizard throws its adhesive tongue accurately at an insect and one-eyed man (Wiley Post) can land an aeroplane. The pelican not only plunges into the water to catch his fish, but has learned, without the benefit of a textbook, to make allowance for the displacement of its prey resulting from the difference of refractive index between water and air. These acts would be impossible unless depth perception were present. Three-Dimensional Vision The visual appreciation of depth in space involves three dimensions and the question arises of how a flat two-dimensional representation on the retina of the eye can yield a tridimensional percept. This question can be answered fairly well, but the phenomenon is no more remarkable than the ability of the organism to extract meaning from a retinal image which is vertically inverted (upsidedown) and laterally reversed (mirror image). As the visual apparatus increased in complexity of structure it also became more specialized in function. Certain areas (foveas*) generally centrally located, became areas of fixation,* enabling the organism to maintain the moving object in the center of its egocentric field. With the advent of a moving head, external eye muscles evolved to hold the eye in a stationary position relative to the object. Early eyes were immovable and the development of movable eyes, particularly in terrestrial forms, reduced the necessity of excessive head movements. In the higher forms the psychological factor of attention became linked to fixation by the fovea; hence the visual attention reflex, which means nothing more than placing the object in the center of the visual field and attending to it. This gives us the cue to direction of the object. Since the objective relations of objects are spatial in character, our perceptions arc fair replicas of the spatial order, even though the retinal images are extremely unreliable in this respect. The appreciation of tridimensionality is mediated by certain specific cues to depth perception which were primarily identified by the painters of the Renaissance period, and thoroughly evaluated later by psychologists. Cinerama projection, like the former "flats," utilizes these cues, but Cinerama has added a type of panoramic vision which is lacking in the "flats." It behooves us to identify these cues before discussing the depth effects on the motion-picture screen. Thaddeus R. Murroughs: Depth Perception 657