Flight has ever been among the classic human dreams. Since motion movies came, this dream has been transposed to the film, and filmmakers started to invent techniques to make airplanes, superheroes and common people fly in a fascinating way.
The very first experiment concerning the flight on a flying vehicle, were the flying carpet in The Thief of Bagdad (1924) and the plane in Flying Down to Rio (1933) on the wings of which a group of girls starts a crazy dance.
While in 1924 the technique used is the ordinary – at that time, of course – rotoscope (in which animators trace over the landscape, frame by frame), in Flying Down to Rio dance we can talk about rear-projection. This artifice comes from silent cinema, in which could not produce satisfiable results due to the absence of the sufficient equipments composed by a rear projector – with an high intensity light and a a movement with claw and register pins – , a translucent screen and a camera with a moving system synchronized with the one of the projector. The projector casts the image on the screen and the foreground scene must be placed between the camera and the screen itself. A side effect is the quality of the background image that used to be weaker then the foreground, an acceptable lack considering that the background image is commonly blurred. The problem is that the projection must be behind the scene, so that the shooting require a quite huge space, as for sure the RKO studio where the plane with the dancing girls flyied.
The reverse approach, called front projection, was used in 1978 for Superman: the Movie. Many years are passed from 1948 series about the superhero from Krypton, in which he succeeded in flying only…turning into a cartoon! A not so nice effect, if you watch it with contemporary eyes.
Fortunately, things goes better in the Richard Donner’s version: the VFX artist Zoran Perisic decides to apply the front projection for the first time to make a person fly, winning the Oscar for the Visual Effects.
This technique requires a two-way mirror in front of the camera, 45 degree rotated. The projector is placed just on the top of the mirror, so that the image is reflected on the scene. Some parts of the image reach the element of the scene, but because of its faintness it is not perceptively reflected. The other parts reach instead the screen, that is made of a special retroreflective material, able to reflect the ray in the same direction of their arrival. The result is that the foreground appears naturally placed on the background. In comparison with the rear projection, the background is clearer and there is no special requirement of space.
After his experience in Stanley Kubrick’s 2001: A Space Odyssey – in which static images were front projected for the landscape -, Zoran Perisic realizes Zoptic, an extension of the equipment of front projection. Zoptic consists in a synchronized zoom lens system applied to both the projector and to the camera, so that they zoom in and out simultaneously. When the projector zoom in, it casts a smaller image, but in the same time the camera zoom in that image so that the background image continue to have the same dimension on the film. The foreground scene instead does not change its dimension, so that is zoomed in. In this way, Perisic can show a Superman that came nearer – becoming bigger on the film – on the background of the sky that continue to have the same distance – the same dimension.
The coming of digital cinema make back in vogue the technique of chroma key compositing: the foreground scene is shooted on a monochromatic panel (commonly a green or blue screen) that will became the matte mask for the background. If in traditional cinema this process consists in removing the mask – with a double exposure or other approaches – and physically copying the cropped foreground onto the background film, in digital cinema a software recognize automatically the mask color and remove it from the frames. For this reason, the chroma key has become one of cheapest VFX techniques, used in flying scene of most of recent movies, such as The Matrix (1990), The Avengers (2012) and the most recent Superman in Man of Steel (2013).