Computing Colorimetric Errors of a Color Television Display System

The colorimetric characteristics of a color television display system are determined by the display primaries, the display white color and the signals applied to the display device. FCC Rules and Regulations state that, for the color television system approved for broadcasting in the United States, the gamma-corrected R,G,B voltages used to form the composite color signal are to be suitable for a color picture tube having primary colors with NTSC chromaticity coordinates. The numerical values of the signal specification assume that the display white color will be CIE Illuminant C. (x = .310, y = .316) Most color picture tubes in use at present (1974) have phosphors whose chromaticity coordinates differ substantially from NTSC primaries. If the signals applied to such picture tubes are those formed by color decoding which is the inverse of NTSC encoding, substantial colorimetric errors will result. These errors can be reduced by a corrective matrix which may be introduced directly or by modifying the color decoding.