academy aperture/academy frame The standard frame mask established by the Academy of Motion Picture Arts and Sciences in 1932. A ratio of width to height of 4:3, or 1.33:1.

(Stagecoach, 1939)

The ratio between the height of the projected image and its width—the aspect ratio—is dependent on the size and shape of the aperture of the camera (and of the projector) and, as we shall see, on the types of lenses used. But it is not solely a function of the aperture. Early in the history of film, an arbitrary aspect ratio of four to three (width to 5 height) became popular and was eventually standardized by the Academy of Motion Picture Arts and Sciences (so that it is now known as the "Academy aperture" or "Academy ratio"). This ratio, more often expressed as 1:1.33 or simply as the 1.33 ratio, while it was undeniably the most common ratio, was never really the sole ratio in use. Filmmakers—D.W. Griffth is especially noted for this—often masked off part of the frame in order to change the shape of the image temporarily. When sound was developed and room had to be made for the sound-track on the edge of the film, the square ratio was common for a while. A few years later the Academy shrank the amount of space within the potential frame that was actually used in order to regain the 1.33 ratio, and this standard gradually developed a mystical significance, even though it was the result of an arbitrary decision. Most film textbooks, even today, connect the 1.33 ratio with the Golden Section of classical art and architecture, a truly mystical number expressive of a ratio found everywhere in nature, often in the strangest places (in the arrangement of the seeds of a sunflower, for example, or the shape of a snail's shell). The Golden Section is derived from the formula a/b = b/(a+b), where a is the length of the shorter side of the rectangle and b is the length of the longer. While it is an irrational number, the Golden Mean can be closely approximated by the expression of the ratio of height to width as 1:1.618. This is very close to the most popular European widescreen ratio in use today, but it is certainly a far cry from the 1.33 ratio of the Academy aperture. While the Academy ratio, arbitrary as it is, was really only dominant for twenty years or so (until 1953), it was during this time that the television frame was standardized on its model; and that, in turn, continues to influence film composition. Since the 1950s, filmmakers have been presented with a considerable range of screen ratios to choose from. [from: Monaco]