A cue mark, also known as a cue dot, a cue blip, a changeover cue or simply a cue is a visual indicator used with motion picture film prints, usually placed on the right-hand upper corner of a frame of the film. Cue dots are also used as a visual form of signaling on television broadcasts.
A pair of cue marks is used to signal the projectionist that a particular reel of a movie is ending, as most movies presented on film come to theaters on several reels of film lasting about 14 to 20 minutes each (the positive print rolls, themselves, are either 1,000 feet or, more commonly 2,000 feet, nominally 11.11 or 22.22 minutes, maximum, with more commonly an editorial maximum of 10 or 20 minutes). The marks appear in the last seconds of each reel; the first mark, known as the motor cue, is placed about 8 seconds before the end of the picture section of the reel. The second mark, known as the changeover cue, is placed about 1 second before the end. Each mark lasts for precisely 4 frames (0.17 seconds).
Coded Anti-Piracy is a different kind of mark, used for watermarking to detect and prevent copyright infringement.
The exact placement of cues varies somewhat from lab to lab.
According to SMPTE-301 (Theatre Projection Leader), there shall be 4 frames of the motor cue, followed by 172 frames of the picture, followed by 4 frames of changeover cue, followed by 18 frames of the picture. That puts the motor cue at frames 198–195 from the end of the picture section of the reel (12.34 to 12.15 feet; or 12-foot-6-frames through 12-foot-3-frames), and the changeover cue at frames 21–19 from the end (1.31 to 1.18 feet; or 1-foot-5-frames through 1-foot-3-frames). As of January 2005, most domestic United States release prints follow this standard.
According to SMPTE-55 (SMPTE Universal leader), there shall be 4 frames of the motor cue, followed by 168 frames of the picture, followed by 4 frames of changeover cue, followed by 24 frames of the picture. That puts the motor cue at frames 200–197 (12.47 to 12.28 feet; or 12-foot-8-frames to 12-foot-5-frames) from the end of the picture section of the reel, and the changeover cue at frames 28–25 (1.75 to 1.56 feet; or 1-foot-12-frames to 1-foot-9-frames) from the end. Prior to January 2005, domestic United States release prints printed by Deluxe Laboratories (about half of domestic first-run major releases) followed this standard.
Most cue marks appear as either a black circle (if the physical hole is punched out on the negative used to make the projection print of the film) or a white circle (if the mark is made by punching a hole or scraping the emulsion on the positive film print). They will also appear as an oval if the print is projected through an anamorphic lens.
In order to make these marks appear clearer to the projectionist, the punched film is most often "inked" after punching by application of India ink, or a similar ink. The sample frames at the right have very fine inking. In the days of three-strip Technicolor, and successive exposure Technicolor cartoons, where separate silver images were available, it was not uncommon to apply two punches, one being larger and circular and the other being smaller and "serrated", with these being done in contrasting colors.