Aspect Ratio

The ratio of an image’s width to it is height. It is commonly expressed as two numbers separated by a colon, as in 16:9. For an x:y aspect ratio, the image is x units wide and y units high. Widely used aspect ratios include 1.85:1 and 2.39:1 in film photography, 4:3 and 16:9 in television, and 3:2 in still camera photography.  Today, 16:9 is the most common ratio.