Picture-sound distance

from Wikipedia, the free encyclopedia

The picture tone distance is a term used in film technology . It is the standardized distance from the picture window to the pickup for sound films (COMOPT or COMMAG). The sound acceptance point contains the components required for the respective sound system ( optical sound or magnetic sound method ).

The distance is technically necessary because the image projection requires an intermittent film transport, ie standstill during the projection while the sound track has to be continuously moved past the sound head. To compensate for this, loops are stretched into the film. Thus, the film image and the associated sound cannot be side by side. For this reason, the audio information in the respective mix is ​​only combined with the video film after the finished image cut: by recording the magnetic sound edge track or making a sound negative and making optical sound copies.

For normal film with optical soundtrack, the image tone distance is 20 film steps or 380 mm. The tone preference on the projection positive should be 21 film steps ± ½ (ISO 2939). With a difference of one film step or 1/24 of a second, a point-synchronous impression is achieved at a distance of about 14 meters from the screen and loudspeakers. It's about balancing the speed of sound and the speed of light. The prerequisite for this synchronous concept is that the projectionists clamp the film exactly on the hole . With COMMAG normal film, mainly CinemaScope copies, the picture-sound distance is 28 film steps in the other direction. There is no international standard in force for this.

With narrow film 16, the scanning distance for optical sound is 26 film steps, for magnetic sound 28. With normal 8 film, the standard specifies 56 ± 1 film steps, with Super 8 and Single 8 it is 18 ± 1 film steps for magnetic sound, 22 ± 1 for light tone.

literature

  • ISO 490
  • ISO 1201
  • ISO 2404
  • ISO 2939
  • ISO 3027
  • ISO 4243
  • ISO 4244
  • Uwe Ney: Modern Narrow Film Practice. Equipment, script, recording, editing, scoring . Falken Verlag, Niedernhausen / T. 1981, ISBN 3-8068-4043-1 .
  • US Patent 1,833,015A, therein 100 feet or a good 30 meters projection distance as an assumption

Web links