Journal of the Society of Motion Picture Engineers (1930-1949)

tained by a person sitting comparatively close to the screen. In a stereocinema, distortions are usually least at a seating distance of 2 to 2.5 W, and if — but only if — the picture has been shot so as to be acceptable from this position, it will not as a rule appear unnaturally elongated even if viewed from much farther away. This is due to the inverse effects of mb and mw described under the heading "Binocular Magnification," earlier in this paper. Practical viewing experience reveals a substantial constancy in the depthappearance of the image between the front and back seats of any normal theater; but this will only be true if N values of 2 or more are employed continuously, for otherwise the distant spectator will become conscious of the gap existing between himself and the screen. In our experience, provided that a sufficiently high level of technical perfection is achieved in the production and projection of a 3-D film, nearness values as high as Ns can be held continuously (for example, in a stereo window), with much larger values for the normal duration of an especially dramatic scene. Granted, then, that the scene in The Black Swfln will be framed in an N2 window; and that the audience, though for the most part unconscious of this fact, will be aware of seeing a picture totally different from the normal one, and different too from a stereo film presented wholly behind the plane of the screen. Granted this, what else will the audience be aware of? In the first place, the fact that their eyes can now scan the scene in depth means that the visual content of each shot will be much increased, and this in turn necessitates holding the shot longer on the screen. Today, when few audiences have seen 3-D films before,, quick cutting is ineffective, since each shot takes an appreciable time to establish itself, after which its quick disappearance produces an effect of disappointment and even annoyance. This is an extension of the principle on which color films tend to be cut somewhat slower than black-and-white ones. Secondly, the audience will be much more aware of the importance of depth relationships in a scene. Figure 10 shows a shot in The Black Swan which is of a type particularly impressive in 3-D. Whereas in a flat film it would achieve no more than the normal effects of deep focus, the third dimension gives the foreground figure an almost physical effect of size and massiveness. Even when the spectator is consciously watching the White Swan trying to make her presence noticed, he feels his eyes drawn to the menacing figure of the Enchanter standing much closer in the foreground and trying to banish her away. In the third place, the audience almost completely loses the impression that it is watching the photographic rendering of a scene. Actual reality seems to lie before it, and when the film is in color this reality is almost complete. Thus in the first scene we have been considering, the Male Variation danced by John Field will appear almost as if one were present in the theater. The raising of the banners right in front of the eyes produces by contrast a momentary feeling of complete surprise; and after a brief pause, the successive lifting of four pairs of banners out of scene — flowing in the same unbroken rhythm — disguises the fact that the scene has changed and thus introduces an element of fantasy when both a new decor and a different dancer are revealed. Part III: A Critique of Existing Procedures It may well be asked how, in the absence of a general transmission theory, proper camera and projection conditions could have been set up for the stereoscopic films produced up to now and those in current production by other 274 October 1952 Journal of the SMPTE Vol. 59