Transition Effects in Compatible Color Television

Perfect reproduction of a scene by color television requires that three independent colorimetric quantities be known for each point of the picture. The particular three quantities chosen to be transmitted and the bandwidth assigned to each are among the system variables which must be specified. The optimum choice of these parameters is decided principally by subjective rating of the reproduced color picture with particular regard to color and luminance transitions at boundaries in the picture content. This paper describes an experimental video frequency color television system in which these variables can be isolated and conveniently studied. With this system the make-up of color difference signal packages and their assigned bandwidths are switchable so that an observer can view in sequence and on the same display a picture transmitted utilizing various signal forms. Investigations using this system suggested that certain undesired luminance variations were the most objectionable feature in the reproduction of the color transitions, and led to the development of a means for predistorting the luminance signal to compensate for these variations in the reproduction. This device will be described in the paper.