The proportion of a work of art is pivotal to a composition because it will determine the series of visual relationships between the length and the width of the rectangle as well as the inherent subdivisions. Very few people have the ability to identify proportions of a rectangle by simple observation - usually, analysis and measurement are required. To calculate the proportion of a work of art or any image, divide the larger number by the smaller number, and that will give you the proportions of the rectangle. For example, in the painting below, by Eric Armusik titled "Father Time," the dimensions are 18x24. If you divide the number 24 by 18, the proportions are a 1.3 rectangle.
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