Considerations on light and colour for TV broadcasting

In a recent teaching experience within the Master in Lighting Design & LED Technology of Politecnico di Milano, the students had the opportunity to visit the production studios of Mediaset and to attend a lesson on the use of light in television spaces. The subject is undoubtedly fascinating, having its roots in the art of illumination of classical theatre, up to new approaches and technologies, such as automated mobile lights and LED light sources. The approach to lighting for the TV differs (albeit with some significant overlap) from the more traditional architectural lighting; the organization of the workgroup, the design processes and the tools used, the objectives to be expressed with the light and the strategies to achieve them, the available technologies and above all, the colour control of the lighting envelope. Lighting for television spaces (but also for movie industry) is based on the assumption that the final observer is not the human being as for the architectural sector, but the camera. The digital eye of the camera does not have the internal dynamics of the human visual system; it does not have the same automatic adaptation and correction mechanisms, although technology allows numerous operations to control the parameters related to colour. Based on this assumption, the indices commonly used for the human observer such as the CRI or TM-30 are also not adequate for an evaluation of the sources (or lighting systems) for television and cinema applications. The purpose of this contribution is not to cover all the techniques for the lighting of television studios (extensive topic) entirely, but to collect a right amount of information relating to the operations on light and its chromaticities, such as correction and indices used for the colour temperature or the limits and possibilities given by the new technologies.