SMPTE RP 221 – Specifications for Extraction of 4 x 3 Areas from 16 x 9 Images for Television Systems
This practice describes how to extract 4 x 3 aspect ratio images from the center of a 16 x 9 aspect ratio television picture. This practice is intended primarily for nonscripted or line television productions where it is impractical to use pan and scan techniques to track the areas of interest in the picture. Protecting the 16 x 9 picture for a 4 x 3 extraction will guarantee that the parts of the picture where action occurs will exist in the 4 x 3 cropped picture.
