The measurement of the colorimetric fidelity of television cameras

Abstract

The broadcast television engineer needs to assess the overall performance of colour television cameras. This requires many measurements of electrical and optical performance and, not least of all, measurement of the fidelity of colour reproduction. Until recently, measurement of colour has not generally been a routine procedure for either acceptance testing or during maintenance. It is, however, necessary that performance is known in respect of the absolute reproduction against an original scene and, perhaps of greater importance, the matching of reproduction of cameras from the same or different camera suppliers. Broadcasters throughout Europe have been investigating methods of objective colour measurement and these activities have been co-ordinated by the European Broadcasting Union (EBU) to the extent that in 1987 a recommendation was made for procedures of measurement of the colorimetric fidelity. Two methods were recommended, the Spectrophotometric method and the Real Sample method. The former requires the full spectral analysis of the camera from which reproduction of a set of test colours is computed, whereas the latter measures the actual camera reproduction when imaging a calibrated set of the test colours. Both methods are compatible and can give an overall quality assessment of colour reproduction.