Know your Leaders....

Whatever head and tail leaders may have been used on cutting copies during editing stages, a set of one of the standard types must be attached during the final negative cutting operations so that they will be reproduced in all subsequent prints. They have a three-fold purpose:
1. to provide protection against damage during handling and transport to both ends of the roll of film;
2. to identify the subject by it's title, part number, language version and other details;
3. at the head end, to indicate the position of the film in the picture gate and sound head for correct projector thread-up and the timing for correct operation.
The protective section of the leader is usually provided by a 6 to 8 foot length of waste raw stock or blank processed film joined on to the beginning and end of the copy but the identification and synchronising sections must be printed from the assmbled picture negative. Leaders for sound track negatives are blank throughout the synchronising section, but carry identification wording scribed or printed in the track area to match that of the picture.

The general form of leader originated by the American Academy of Motion Picture Arts and Sciences in the 1930's is still widely used in general cinematographic practice. After the identification section giving the subject name and part number, the first part of the synchronising section shows frames marked 'picture start' and '35mm sound start' at a seperation of 20 frames, corresponding to the projector picture gate and sound head. From the picture start frame to the first frame of the picture is a distance of 192 frames (12 feet in 35 mm), printed as opaque black except for a series of clear frames with black numbers 11 to 3 at 16 frame intervals. Symbols to represent the sound head thread-up frame corresponding to these numbers appear 20 frames in advance of each. The last 47 frames of the leader immediately preceding the first picture are printed in black throughout.

At the tail end of a B reel, the last picture is followed by 48 black frames, known as the run-out leader, after which comes the final part title and identification. The tail end of an A reel and the head of a B reel if printed seperately carry frames marked 'splice here' to indicate where te two sections are to be joined for final projection.

SMTP Leader

Although well established in regular motion picture projection practice, the Academy leader was not considered to provide sufficient accuracy of timing for television operation and the appearance of single clear frames of numerals in otherwise black material was found distracting. In 1965 the Society of Motion Picture and Television Engineers (SMTP) therefore intoduced a new pattern of leader to improve these points and it was hoped that this would become universal for both theatrical and television practice. This leader introduced a number of new features especially in the synchronising section.
The synchronising numbers are now shown in every frame from the Picture Start up to the final run-in 47 frames, each number from 8 to 3 appearing as a black figure on a medium density background for a length of 24 frames, or and second's duration at 24 p.p.s. As an aid to accurately timed operations, a radial line rotates over the background once every second while each number appears, showing a change of background density as it moves. The last frame of the count-down numerals, shows the figure '2' and is followed by 47 frames of uniform density but not opaque black. At the tail end, the run-out section immediately after the last picture is extended to 87 frames of similar uniform low density.
Frames showing 35mm and 16mm photographic sound head positions relative to the the picture start frame are included, and in addition frames in the numbered section are identified 'M 70' and 'M 35' to indicate the magnetic sound start positions for 70mm and 35mm prints.

taken from: Motion Picture Film Processing, 1985, Dominic Case, Focal Press