Colorization is a computerized process that adds color
to a black-and-white
movie or TV program
The process was invented by Wilson Markle and was first used in 1970 to add color to monochrome footage of the moon from the Apollo mission. In 1983, Markle founded Colorization, Inc. The word "colorization" soon became a generic name for the adding of color to black-and-white footage.
The process of colorizing a movie begins with a monochrome film print, preferably a new print struck from the original negative. From the film print, a high-quality videotape copy is made. Technicians, aided by a computer, determine the gray level of every object in every shot and note any movement of objects within shots.
A computer adds color to each object, while keeping gray levels the same as in the monochrome original. Which color to use for which object is determined through common sense (green for grass, blue for the ocean) or by investigation. For example, movie studio photographs or costume vaults may provide guidance as to what color a hat should be. In cases where no such guidance is available, colorists pick their own colors, presumably with some aesthetic sensibility.