There are a number of factors which make video difficult to define as a system of production: the novelty of the medium, the diversity in the level of complexity of the various video formats, and the flexibility of video as a means of recording. But perhaps the most crucial is the general fluidity between the three major audio-visual systems of film, television, and video. Film can be transferred to video tape and video to film, television can transmit live, filmed, or video-taped material indiscriminately, film can be used to record the output of a television studio (indeed before the application of video tape in the late 1950s it was the only such recording system available). In particular video, the third of the systems to come into existence, is able to reproduce perfectly the production patterns of the earlier ones to which it is heir. Nevertheless, despite these overlaps, it is possible to make clear and revealing contrasts between: firstly, the production system adopted almost universally for the making of feature films and film documentaries; secondly, the production system essential to television studio

broadcasting; and thirdly, the specific system of video which, in addition to its ability to copy, has features missing in both the others.