Film

• Even today, film cameras do not record sound the way digital cameras and consumer camcorders do. A film camera simply records moving images onto a film strip, the contents of which are connected to a separate audio recording much later in the film production process.
  
  

Early Cameras

• Before the advent of sound film, it was not necessary for cameras to record images at a precisely constant speed. Early cameras often ran at variable speeds, meaning that the projected film would very slightly speed up and slow down as people watched it.
  
  

Syncing Sound and Picture

• For the sound and picture of a film to be in sync, it's necessary that both the camera and audio recording equipment run at a precise and constant speed; otherwise the audio will drift out of sync over time. For standard film, this speed is 24 frames per second (FPS).
  
  

Sync Sound Camera

• A sync sound camera is one capable of providing sync sound--one that runs at a constant speed. Modern sync sound cameras usually run on a quartz crystal motor--the same kind used in a quartz watch--to ensure a constant 24 FPS.
  
  

Wild Sound

• Sometimes, additional sound is recorded "wild"--that is, unsynced. This sound has to be manually and painstakingly synced up with the relevant images in the editing bay, during film postproduction.