Aspect ratio frames the scene
Aspect ratios are proportions expressed as width to height (x:y). The most common aspect ratios used today in movie theaters are 1.85:1 and 2.39:1. Two common video aspect ratios are 4:3, universal for standard- definition television, and 16:9, universal for high-definition television and European digital television.
The controversy over aspect ration has to do with converting theater films to television. Two methods are used: the much despised pan and scan, and the “letterbox” format that adds black space above and below the frame to maintain the correct aspect ratio.
Director Sidney Pollack talks about why he avoided wide-screen aspect ratios for many years.