Clock leader

Attached to a film intended for projection or copying, comprising picture and sound information, timing and start marks.

There have been many forms of clock leader added to the head of film. The leader originated by the American Academy of Motion Picture Arts and Sciences in the 1930s is still widely used in general practice. This has a ‘Picture Start’ and ‘35mm Sound Start’ at a separation of 20 frames followed by a count down from ‘11’ to’ 3’ at 16 frame intervals.

In 1966, the SMPTE along with the ASA introduced a version (PH22.55-1966). This standard specifies the make-up or assembly of leaders and cue marks for 35 mm and 16 mm sound motion picture release prints for use in both motion picture theatres and television studios.

This SMPTE version has synchronising numbers appearing continuously with the numerals ‘8’ down to ‘3’ repeated for 25 frames with a rotating wedge (increasing at 15°per frame) in the background.

The figure ‘2’ is then followed by 47 frames of black. This is then spliced onto the picture. Frames showing the sound head position for 35 mm and 16 mm relative to the “Picture Start” are also included for syncronising sound components prior to printing.

This standard also details ‘motor’ and ‘change-over’ cue marks for 35 mm and 16 mm sound motion picture release prints. The EBU and ISO have also introduced leaders along similar lines.