The aspect ratio of an image describes the proportional relationship between its width and its height. It is commonly expressed as two numbers separated by a colon, as in 16:9. For an x:y aspect ratio, no matter how big or small the image is, if the width is divided into x units of equal length and the height is measured using this same length unit, the height will be measured to be y units. For example, consider a group of images, all with an aspect ratio of 16:9. One image is 16 inches wide and 9 inches high. Another image is 16 centimeters wide and 9 centimeters high. A third is 8 yards wide and 4.5 yards high.
You’ve heard the term before. You may have even used it in explaining to your frustrated elders why certain programs on television are cropped, and why others fill their entire screen. Aspect ratios have evolved with camera technology, taking film and television from literal small screens to IMAX and beyond.
The following video is called The Changing Shape of Cinema, in which filmmaker “John Hess traces the evolution of the screen shape from the silent film days through the widescreen explosion of the 50s, to the aspect ratio of modern digital cameras.”
If you’re at all interested in the more technical aspects (pun: intended) of filmmaking, this may be interesting for you to watch. Just as colour became a watershed moment, or high density pixel ranges have become an expectation of quality, this brief history lesson will prove aspect ratios of similar importance.
Source: First Showing