This invention concerns a system for the distribution of films by electronic means, and in particular, for ensuring a director's intended rendition of the images is attained in differing viewing conditions and technologies. Thus master data enabling the luminance and chromaticity of every part of every frame as previously displayed in a first display environment to be determined may be modified to achieve a similar subjective effect in a second display environment, the modification depending for example on data characterizing the said second display environment.