E-cam

Rediffusion Television has pioneered yet again with the development by its staff of E-cam. This stands for electronic cameras, a system of using film cameras in the same way as television cameras but recording the end product on film instead of tape While other organisations have worked on the system with single cameras. Rediffusion Television was the first to make a film in TV studios using an integrated, multi-camera system. In pilot experiments scenes from the play ‘The Small Rebellion of Jess Calvert’ were recorded on film besides the production of ‘George’s Room’ in colour.

The development team, under Mike Spooner, was led by Geoff Pryke, supervisory engineer, planning, and consisted of Bob Warren, Dave Johnson, George Jackson, Eric Ruckle, Jack Nichols, Peter Koller, Jim Beasley and Dave Skeate.

Great assistance was given by Jim Crossley and Jim Runkel throughout, and also involved of course, was mike metcalfe, engineer-in-charge, E-cam ops., the author of this article.

 

The concept of E-cam was born from a desire to produce high quality film programmes by television methods. If this long standing dream of programme producers could be realised, it would not only reduce production costs, but would overcome the serious technical problems associated with the international exchange of programmes for television.

The varying line standards of the television systems used throughout the world severely inhibit the free exchange of programmes, and a conversion process is necessary before material recorded in one country can be played back in a country with different line standards.

Originally the conversion process was an optical transfer, and in essence, consisted of a television camera on one standard, viewing programme material displayed on a monitor of a different standard.

Later developments have removed the optical transfer and are purely electronic with consequent gains in picture quality. The system works well for black-and-white material and can be used for live or previously recorded programmes.

The future interchange of colour programmes, however, presents an acute problem. Not only must consideration be given to the line standards of the countries concerned, but also the system of colour television employed, there being several in current use throughout the world and variants of each.

Programmes on film however, do not suffer from these technical limitations as the telecine machine used to transmit a film is already working on the required system and so the process becomes automatic.

This applies to both black-and-white and colour films – if the telecine is colour equipped of course – and removes completely the problem of conversion and colour system compatibility. Since all television stations possess telecine equipment, film has become the universal currency of programme exchange. However, film making by traditional methods can be long and expensive compared with television, and various ways have been sought to combine the best of both techniques.

The idea of coupling a television camera to a film camera in order to monitor the scene remotely and to facilitate the control of several cameras simultaneously is not new. A photo-recording system was devised in 1955 by Dumont in New York in collaboration with Arnold & Richter of Munich, and although it had limited success, it nevertheless showed the value of the concept. Since that time, several systems, using both 16 and 35 mm. film in various configurations have been developed, each having its own particular advantage. In the latest development of Electronicam the film camera used, a well tried Arriflex 35 mm., has been developed by Arnold & Richter from the original prototype system of 1955. The television channel using a Plumbicon picture tube and embodying the latest circuitry, was produced by Fernseh in collaboration with our own engineers, to a first-class broadcasting specification.

Briefly, the system works as follows. Light from the studio scene is focused by a zoom lens on to the film in the camera gate. A specially designed reflex shutter in front of the film gate has two reflecting segments. These mirrored sections allow a proportion of the available light to be reflected through a suitable system of correcting lenses into the Plumbicon camera attached to the side of the film camera.

The two mirrored sections of the shutter are of equal area, one operating during film pull-down and the other during film exposure. The shutter revolves at a constant speed of 25 frames per second, giving the two equal exposures per revolution necessary, one for each field of the television picture. The mirror segments are so arranged that the film receives full exposure at ¹⁄₅₀ sec.

The television picture, therefore, is an exact replica of the scene viewed through the film camera lens and is available to a monitor viewfinder mounted at the back of the camera. The cameraman uses this viewfinder in exactly the same way as in a television camera and has normal control of zoom, focus and framing etc. The television picture is also available to monitors in the various control rooms.

The method of operation follows closely that of a standard television studio production. Pictures from all cameras are permanently available to the director whether the film is running or not. Rehearsal takes place in the usual manner and film is only exposed for the actual transmission/take. During rehearsal when film is not being exposed, an estimate of the amount of film to be used during the subsequent take is indicated by footage counters, one for each camera, displayed on the control desk. Careful pre-planning ensures that the sequences are arranged for the most economical use of each camera’s 1,000 ft. magazine of film (approximately 10 minutes running time) and that no camera runs out of film during the take. The actual transmission/take is accomplished by pressing the appropriate button on the simple vision mixer panel which starts the film camera and switches its television picture to ‘transmission’. Cutting from one camera to another is achieved by pressing the appropriate buttons, and after a delay of approximately ⅓ second, to enable the camera motor to attain speed, the vision is automatically switched and the film exposed.

For fast cutting sequences an extra button is provided enabling the selected cameras to stay running while cutting between them, thus obviating the running-up delay. This method, of course, is wasteful of film and should only be used for short periods. As it is not possible to fade or mix between the film cameras, the vision mixer is a simple ‘cut only’ device. Opticals and other effects are added where required in the film laboratories.

Programme sound is recorded in the normal way on sprocketed magnetic tape running in synchronism with the film cameras. To facilitate the later assembly of the processed film, a cue tone, having a different frequency for each camera, is recorded on the magnetic sound tape on another track alongside the programme sound. These tones are selected automatically by the vision mixer’s cut buttons. During the assembly of the processed film, the cue tones are played back on a synchroniser to identify the camera and to serve as a guide for the assembly of the film.

To allow the lighting director to maintain consistent film exposure, the lens iris of each camera can be remotely operated from the lighting control console. Comprehensive picture and waveform monitoring facilities are available to the exposure controller and the lighting director to enable the close exposure tolerances required for successful colour filming to be maintained.

By close control of the electronics (which require a high degree of stability) the television camera can be used as an exposure meter and the high definition pictures from it give a continuous indication of what the film is recording. The system is equally capable of filming in colour or black-and-white, and it is in its colour role that its greatest virtue will become apparent. At a time when the complexity of interchanging colour programmes recorded electronically is becoming apparent, the E-cam system can be a vital link in the chain of international programme exchange.