Film leader
A film leader is a length of film attached to the head or tail of a film to assist in threading a projector or telecine. A leader attached to the beginning of a reel is sometimes known as a head leader, or simply head, and a leader attached to the end of a reel known as a tail leader or foot leader, or simply tail or foot. "Film leader", used generically, refers to different types manufactured for many editorial and laboratory uses. For example, some types are used in negative cutting while making A and B rolls for  printing. "Painted leader" is perforated film in overall colors, usually white, black, red, blue, or green. These are used for protective head and tail leaders to keep the body of the program material from being damaged. "Fill leader" (also called picture fill, or spacer, or slug film) is used to space out different sections of magnetic audio film stock so they are kept in synchronization with the picture. Typically, this is made from rejected or retired prints of previously released programs. A universal film leader is a head leader designed for television and theatrical motion picture exhibition applications. This includes  the countdown, and technical information about the film, including title, studio, production number, aspect ratio, sound level and mix, reel number and color. Head leaders are marked with visual and audio information that may be used to ensure that the correct amount of time is allowed for the machine to run up to speed and arrive at the beginning of the program or movie. They generally feature a countdown. Countdown leaders. Two versions of the countdown leader are well-known: The latest overall length of both styles is the same: in 35mm, 16 feet and 4 frames or 260  frames. The countdown section begins with a single frame bearing the words "Picture Start." The sync beep (or 2-pop) occurs in synchronization with the last numbered frame ("3" on the Academy leader, "2" on the SMPTE Television leader). The length of the countdown section, including the "Picture Start" frame through to and including the "3" foot or "2" second frame, is 9 feet and 1 frame (145 frames) plus 47 frames of black (for a total of 12 feet even or 192 frames). In 2013, SMPTE introduced the D-Cinema Digital Leader; a picture version of the countdown leader  for use with Digital Cinema Distribution Master (DCDM) files. The DCDM is the penultimate step to the creation of the Digital Cinema Package (DCP). Unlike the previous film standards, no provision is made for changeover cue marks because digital cinema files are continuous.