His on film

His film is opposed in the history of cinema to the various processes of sound on record , when the sound films were composed of two distinct elements: on the one hand, the film itself as a support for the only photograms (images on the other, a phonographic medium in which various audio elements such as music, sounds, and words were recorded , these processes being based on the simultaneous start of the two reading machines: the projection apparatus and the phonograph to cylinders or discs , orgramophone .

In film sound processes , sounds and images appear on the same “film”, which carries along the photograms one or more optical sound tracks (photographic process) or one or more magnetic sound tracks ( magnetic tape stuck to the film). movie).

If the most developed procedure of its on disk, the Vitaphone , ensures in 1926 the appearance of the first sound films in front of an enthusiastic public (with in particular the Singer of jazz in 1927), the general public world and the industry of the cinema definitively adopt the principle of the couple images and sounds, only with the fundamental advance that represents the sound on film . It was the Fox Film Corporation that, in 1927, took up the principle of photographic recording of sound on film that had been imagined previously – without however being able to make it reliable and to commercialize it – the fertile inventor Lee De Forest . Fox files this process under the name Movietone .

Its optical analogue

“The Movietone sound is said variable density, the recorder has a magnet with two branches between which a tensioned wire is traversed by the modulated electric current from a microphone. The wire diverts according to the intensity of the current and masks more or less a strong light which crosses the two branches. The variations of this light, collected by a lens, impress on the side a film film 35mm. This one, after development, is copied on the film between the images and one of the rows of perforations. Subsequently, this photographic track is reproduced on exploitation copies at the same time as the images. ” 1 The disadvantage of this method is that the sound is altered with the wear of the copy and is to become inaudible, covered by thebackground noise .

Also, in 1928, Radio Corporation of America ( RCA ) launches the sound Photophone which is said to fixed density. “The recorder is equipped with a mirror galvanometer that oscillates according to the variations in the intensity of the current output from the microphone. The mirror is illuminated by a strong light that is more or less returned to a lens that records on film 35 mm the amplitude of the received illumination (flicker). The printing of the copies follows the same process as the Movietone but this process has the advantage over the latter not to deteriorate ” 2 with the wear of the exploitation copies.

In projection, the optical tracks are lit by a thin and powerful net of light coming from a so-called exciter lamp, whose luminous fluctuations generated by the passage through these tracks are received by a photocell converting these luminous fluctuations into variations of electric current that is amplified at the output, thanks to a tube amplifier which feeds at the end of the course the speakers of the cinema room 3 .

Its analog magnetic

But a novelty will change for a time the sound gives on quality film. The magnetic tape, widespread in the 1950s , offers a sound well above that of the analog optical track. The technique is relatively simple: a thin ferromagnetic ribbon is deposited all along the film after developing the images. This is what accompanies 70 mm format movies , with 7 magnetic sound tracks. A special version (“Grandeur” of Fox) returns to analog optical density density for operation in countries where projection devices do not have magnetic readers. The films in the format 35 mmmay be equipped with magnetic sound tracks. And this is the simplest development that is brought to the medium film format, such as 16 mm , and film lovers formats such as 9.5 mm and 8 mm .

The longevity of magnetic sound tracks is however limited to about thirty years, and in any case, the arrival of digital encodings has put an end to this type of sound system. Longest use of sound recorded on ferromagnetic film was format IMAX silver 100 mm , which method sound was independent of the band images.

Its optical color film on

A problem arises with color films: if the sound track is made on this type of film and if it is developed at the same time as the images, its density is low, never reaching a clear opposition between the sound modulation which must to be very white and its bottom which must be on the contrary as black as possible. The color sound is too weak or nonexistent. A perilous solution was found: on the film already developed image copies, a ribbon of photosensitive film productis sunk at the intended location for the sound track (s). He is then impressed by a black and white negative of the soundtrack. This ribbon is in turn developed according to the black and white process. Each color copy is processed three more times after the development of the images. This complexity of treatment has a practical and economic disadvantage: if an incident occurs either at the time of the laying of the silver ribbon, at the time of the printing of the track, or at the time of its development, the image copy is definitely lost.

In 1998, the leading manufacturers of conventional film 35 mm and 70 mm , Kodak, Fuji, Agfa, Technicolor, Dolby and Deluxe, unanimously decide to abandon this multiple treatment for environmental reasons, the products used being particularly harmful in their releases. From now on, the sound track is in color because the researchers have benefited from a technological advance: the invention of the light-emitting diode , the LED. A red LED is able, unlike the incandescent excitation lamp usually used in projection devices, to read perfectly and without loss of data a track on a colored background ( cyan )4 .

Its digital

Positive silver film 35 mm(Widescreen or other). Position of the sound processes on the film: SDS (the two blue areas outside the perforations ), Dolby Digital(gray areas between the perforations, optical track side, with the DD logo in their center), two analog optical tracks (on the right of one of the rows of perforations), along the photograms.

But other technological advances are experienced and will also sweep the use of LED, before being themselves exceeded by the arrival of digital hard drives, both for shooting or projection.

SDS, Dolby Digital, 2 analog optical tracks. On the far right, the linear time code (white dashes) controlling the CD-ROM installed in a separate reader from the projection device).

First, in 1991, an unexpected return of sound on disk in the form of the CD-ROM , launched commercially by Steven Spielberg , uses a timecode read on the tape images, which refers to a CD-ROM drive loaded with a disc that accompanies each copy. picture. This is the DTS ( Digital Theater System) process , also known as Dedicated To Sound . Illustration on the right.

In 1993, SDS ( Sony Dynamic Digital Sound ), launched by Sony , prints on each film edge a digital color optical tape, translated into sound by a digital processor.

In 1994, the company Dolby had the idea to abandon the reading of a continuous track and use the space between each perforation to implant blocks of optical data that a special reader, working at 320 kilobit per second , decrypts one by one to broadcast the soundtrack in the amplifying chain.


  1. ↑ Marie-France Briselance and Jean-Claude Morin , film grammar , Paris, New World ,, 588  p. ( ISBN  978-2-84736-458-3 ) , p.  163
  2. ↑ Briselance and Morin 2010 , p.  163-164
  3. ↑ Lo Duca , Film Technique , Paris, Presses Universitaires de France , coll.  “What do I know? “, 128  p. p.  34
  4. ↑ url = http://www.filmjournal.com/committed-cyan  [ archive ] | publisher = Film Journal International | year = 2004 | viewed on = June 13, 2017

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