Aspect ratio or A.R of an image is the proportion of picture width to height expressed as two numbers separated by a colon. Aspect ratios are mathematically expressed as x:y and x×y. The most common aspect ratios used in the presentation of films in movie theaters are 1.85:1 and 2.39:1. Two common videographic aspect ratios are 4:3 (1.33:1), universal for standard-definition video formats, and 16:9 (1.78:1), universal to high-definition television and European digital television. In still camera photography, the most common aspect ratios are 4:3, 3:2, 16:9. Other aspect ratios, such as 5:4, 6:7, and 1:1 (square format), are also used in photography.