Pal system I phosphor primaries: the present position

In the early days of colour television, the colour-analysis characteristics of the colour camera and the chromaticity of the display phosphors were not critically related, and the original NTSC specification (1953) of phosphor chromaticities served quite well for many years. Improvements in colour cameras of the mid-1960s, and in particular the implementation of negative lobes in the analysis characteristics, made possible much better colour rendering. For this to be achieved, however, the camera analysis had to match the chromaticities of the phosphors in the display tube, otherwise the potential improvement became an impairment. To consolidate these advantages, and to facilitate programme exchange, the EBU decided to standardise the Pal System I on a set of chromaticities consistent with available display tubes (which had for some time differed markedly from the NTSC phosphor primaries). The CCIR ratified this standard in 1974. A brief history is given describing how these changes came about. The implications of this standardisation for the broadcaster are examined, and the modern practice of matrixing the input signals to the monitor is described in some detail.