3/2 Pull Down

Another of those dreaded sync terms. One of two types of pull down pertinent to synchronization, and the two get confused quite often. We’ve already discussed what pull down is (see WFTD Pull Down); 3/2 pull down is a specific type of pull down employed when film is transferred to videotape. The problem is that film is generally shot at 24 FPS (frames per second) and video in the United States is generally around 30 FPS. It is desirable to have each film frame correspond to a video frame, but because they operate at different frame rates, this is impossible. It is also not acceptable to speed up the film to video’s 30 FPS during transfer to video (unless it’s one of those old Charlie Chaplain movies). The best compromise has been to employ 3/2 pull down during the telecine transfer, which reconciles the 24 FPS of film with the 30 FPS of NTSC video by scanning in the second field of video twice on every other frame of film. This effectively creates an extra 25% of visual filler to occupy the six extra frames of video that occur each second. Amazingly, this process is pretty much undetectable to those who aren’t looking for it and is the way film has been transferred to video for many years now.