Colour performance of the Secam colour television system

The Secam colour television system has many parameters in common with the N.T.S.C. system, but the constraints imposed on the reproduction of both large-area colour and colour transitions by the practical limitations on amplitude and frequency excursions are different. After discussing the parameters of the Secam system which have been assumed throughout the paper, the relationship between the chromaticity of the transmitted colour and the modulation of the subcarrier is considered and compared with the relationship which exists for the N.T.S.C. system. In particular, the effect of luminance level on the gamut of reproducible chromaticities is examined, and it is shown that the frequency limitations on the deviation of the Secam subcarrier are not important in so far as they might be expected to limit the practical colour gamut. The chrominance resolution of the system is discussed, and the use of an asymmetric passband for the colour subcarrier is suggested. The effects on the colour picture of some types of signal defect are mentioned.