Our actors cannot talk, so we must record the dialogue before we start to shoot the film. The soundtrack is played back as the film is being shot and in order to synchronise the movement of the mouth with the words, we had to devise a method of electrically connecting the puppets’ heads with the tapedeck amplifier and also, of course, a means of ensuring that the right puppet 'speaks'.
Thunderbirds and its predecessors make considerable use of special effects: up to 50 per cent of the film may be thus classed. We shoot the special effects and the activities of the puppets separately, on different sets, to avoid problems of scale. An airliner exploding in flight, for example, may be no more than six inches long or so. Special effects are, of course, the star attraction and since everything is shot in the studio, there is a big and unceasing programme of model and landscape-building. Even a storm at sea must be shot on the stage in a tank – an overflowing one to prevent a false 'horizon' – with fans creating a force 9 gale and arc-welding equipment providing the lightning. Explosions provide much of the excitement — during shooting as well as in the finished film. The special effects department is continually devising new kinds of explosions and has quite different recipes for an oil rig blowing up and for the detonation of a nuclear power plant. For fire shots, a man operates a smoke generator — a blowlamp affair that burns refined diesel oil to produce non-hazardous fumes… When the palm trees sway, it’s a fan operated to create the breeze…
Special effects scenes are filmed at up to 120 frames a second, compared with the 24 frames a second of normal cinematography, which has the effect of greatly slowing down motions, so that, for example, the explosion of an egg-cup full of gunpowder lasts as long as the explosion of a 1000lb. bomb, and thus appears to have the same magnitude… Sound is constantly a problem in all these special effects. What, for example, is the sound made by a nuclear powered vehicle whilst travelling through space? None at all, perhaps: but while silence used sparingly can heighten the drama, noise of some kind usually improves the atmosphere of this kind of film. So the effects department is kept busy recording sounds appropriate to machines and vehicles that so far exist only in the hands of the model maker.
An early optical problem with the photography was parallax, arising out of the close-range photography the work needed. A director of live actors can stand beside the camera and obtain virtually the same view as the cameraman. When the actors are but a foot or two from the camera, anyone alongside gets a view of the scene quite different from that of the cameraman himself. So director, art director, set dresser, and so on, had to queue for a look through the camera lens — a time-consuming business.
Even worse off were the puppeteers, who operated from a bridge seven feet above the set. For one thing, they could not see the puppets’ eyes, so the camera crew had to shout directions until puppets who were conversing were looking in the appropriate direction. The answer, as we found, to both difficulties is a small television camera, looking into the camera’s eyepiece, with monitors set in suitable positions.
This idea has since been adopted commercially, and equipment with these electronic viewfinders should soon be available. The next step for us will be to record on to videotape, which we shall be able to play back immediately to check for faults.
There are still many things we would like the puppets to do — have more mobile features, for example, and more live hands. While wires remain our main communication we are very restricted but have hopes soon of introducing radio control, to broadcast instructions via a receiver in each puppet’s head. The scope for technical development is immense, in a field that fascinates us at the studio no less than it satisfies our audience.