The image and the sound. Principle of CinemaScope

The image and the sound

Principle of CinemaScope

The image and the sound

The silver film was created in 1889 in 35 mm width with two rows of lateral perforations. Today, the 35 mm remains the standard format, but others are born, narrower like 8 mm and 16 mm, or wider like 70 mm. The panoramic image is not necessarily obtained with a wide film. The Vistavision, for example, only uses 35mm film, but the image is inscribed in its length. The Cinemascope also uses the 35 mm: when shooting, a vast field is filmed and a special objective, called "anamorphic", compresses the image between the perforations; at projection, the same lens renders the image on a widescreen.

Film films are essentially negatives, intermediate films then allowing the drawing of positive projection copies. Moreover, today's shootings are almost exclusively in color. All the processes (Technicolor, Eastmancolor, Fujicolor, Gevacolor) are based on the same principle as the photo: the superposition of three layers of emulsions respectively sensitive to red, green and blue.

Sound reproduction

Since the birth of the talking cinema, the sound is recorded photographically on the film. To understand the process, remember that, in a microphone, the sound intensities are transformed into proportional electrical intensities forming a modulated current, the audio signal. In cinema, this current, in turn, serves to modulate the width of a luminous brush, which impresses the film on a track of variable width. Inside the projector, the reverse process is performed to recreate the audio signal.

With widescreen films, the optical track is most often replaced by several magnetic tracks; these allow stereophony as well as special sound effects.

Shooting and projection

Camera

The camera, called a camera, is directly derived from the camera. Like him, he has a lens, a viewfinder and sometimes a photocell. The camera further includes a motor driving the film according to a technique for photographing a continuous series of images on a film running at 24 frames per second.

The scrolling movement is jerky: the film is stopped during the shutter opening time and shifts an image during its closing phase. The film is developed in the laboratory, then projected transparently on a screen in cameras that reproduce the jerky motion of the cameras; their shutter hides the projection during the displacement phases and makes it possible only when the film is stopped. The retinal persistence erasing the periods of occultation (completely obscure screen), it is the deciphering of the optical information by the brain which restores the continuity of the movement of the subjects (this one is thus pure illusion).

Two processes, Imax for flat screen and Omnimax for spherical screen, allow to project a film on a screen of 1000 m2 or more, exceeding the limits of the human field of vision; For example, the Geode Omnimax system uses a film with horizontal scrolling of 69 × 48 flat images (more than 6 km of film for one hour of projection).