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The notion that objects occupy three-dimensional space in our physical world is not a cultural construct but a vivid reality. We know this because we can grasp a solid object, feel its contours, and move it from one place to another. Because of this spatial and tactile awareness we make assumptions about our physical environment based on visual stimuli perceived by our stereoscopic vision. In the visual arts, this means that a two-dimensional representation (drawing, painting, photograph, etc.) can imply three-dimensional reality by mimicking its effects on our ocular system. According to Professor Donis A. Dondis, this is done primarily through the use of linear perspective, which is often supplemented by tonal manipulation in the form of chiaroscuro, the dramatic emphasis of light and shadow.
Since perspective and chiaroscuro are extremely representational methods of expressing dimension, photography in particular excels at them. The precision with which the photographic lens can record minute details is unmatched by the eye. However, man-made optics cannot duplicate the human eye's wide peripheral vision without the tremendous distortion of perspective that results when using a wideangle or fisheye lenses.
Gerald Mast argued that the moving image can illicit a sense of dimensionality within the viewer that is simply unattainable by the static image. "The enlarging or shrinking of an object over a period of time or the length of time it takes to travel between two points are two familiar ways of defining terms like 'close' and 'far.'" These changes in scale appear so natural that we forget we are looking at a flat screen. So aside from perspective and tone motion over time is another useful method of representing dimension.
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Though dimension is an integral part of our world and something we can both feel in the space around us in two-dimensional formats such as painting and photography it can only be represented by such illusion. In fact, when more visually striking representations of three-dimensionality have been attempted in film, it hasn't caught on. Films in 3-D have never been more than an oddity. It's as if people are so accustomed to inferring dimension on a flat surface through more conventional means that the 3-D image becomes too hot, bombarding the viewer with more information than they care to deal with.
Another reason that might explain the unpopularity of the 3-D medium is that viewers want to see a realistic image, to be a voyeur in someone else's life, but they do not want to actually become part of what's happening. Three-dimensional format brings the image to close to real life and involves the viewer too much, almost in an accusing way. The safer, more removed aspect of standard film, in which dimension is implied, is more pleasant for the viewer because it removes them from what is going on while at the same point showing them everything. We can make judgments and give opinions without suffering the consequences.
The technical convention of linear perspective is a Renaissance invention. It is a systematic, formalized method of representation that allows the artist or designer to simulate depth with a few scant lines. It operates on the premise that objects appear progressively smaller the farther away they are. Lines that extend out into space converge at one or more vanishing points on the horizon line, which coincides with eye level. Besides the tool of linear perspective, artists and designers also have a broad range of values at their disposal which can be used to imply dimension by means of chiaroscuro lights and darks. Since light travels in straight lines it cannot curve around an object and equally illuminate all its contours. This means that some surfaces of the object will receive more light than others. These variations in the amount of light being reflected from the object's surfaces are observed as different values.
Value enables the artist or designer to fill in the gaps left by linear perspective. For instance, the basic linear information is insufficient in conveying the dimensionality of a sphere. Without tonal information it is merely a flat circle. The fact that light travels in straight lines also results in the phenomenon of the cast shadow. It is through the dramatic emphasis of highlights, reflected light, and cast shadows that chiaroscuro achieves its revelatory function. Since lighting is so instrumental in this technique, changing the placement of the light sources or the number of these light sources can have drastic effects on the representation, as evidenced in the center and rightmost frames of the above triptych. The leftmost frame is the same scene rendered as a simple wireframe with no tonal information. Objects located dramatically above eye level are said to be seen from worm's eye view, while those positioned extremely below eye level are seen from bird's eye view. The decision of which point of view to take within the frame involves more than just aesthetic considerations; it has psychological implications as well. A slender upright object seen from worm's eye view tends to look more massive and stable because it is appears wider at the base and grows narrower from the bottom like a mountain. The same object seen from bird's eye view often looks more minuscule and unstable because it appears narrower at the base and grows wider from the bottom like a top.
Walter Ioos, Jr. 1994. Poster from Film und Foto International Exhibition, Stuttgart, Germany, 1929.
Introduction