Mixed Highs in Color Television

A high-quality color television system could be made by transmitting independent red, green, and blue images of equally high quality. The bandwidth required by this method would be three times as great as that required for a black-and-white picture of equal resolution and repetition rate, regardless of whether the images are transmitted in sequence or simultaneously. Tests made on the human eye, and reported herein, indicate that the acuity for detail residing in color differences is less than half as great as the acuity for detail residing in brightness. Therefore, if the brightness values in a color television system are transmitted with fidelity up to 4 Mc, it is adequate to transmit the individual color values up to only 2 Mc, with a corresponding saving in bandwidth. In the "mixed-highs" system described, each of the three color images uses frequencies from zero up to 2 Mc and the "mixed highs," which carry only the brightness values of the fine detail, use a video frequency band from 2 to 4 Mc. The total width of the video bands then is only 8 Mc instead of 12 which would be required for three identical bands from zero up to 4 Mc. The bandwidth saved by the mixed-highs technique is obtained not at the expense of picture quality, but is a legitimate saving that arises by avoiding the transmission of information which the eye is unable to use.