Film perforations

Do you remember those old movies that you've seen on TV, where there were usually black lines on the edges of the screen, and pops or clicks on the soundtrack at the same time? That's because those movies were made using a machine called a film projector, which required regular sheets of plastic film to play the movies one at a time.

Each sheet of film has tiny, closely spaced holes punched along its edges, representing a quintessential aspect of the technology's design since the late 19th century known as film perforations. Those holes are there to help accurately move the film and pull it through the projector, so the movie can play at just the right speed, and each frame stays in the correct spot on the screen.

The perforations have to be extremely precise, with exactly the same number and spacing of holes, or else the film won't run smoothly as a movie in the projector. The film also has to be wound firmly onto spools so that it won't wrinkle or break, which could also disrupt the film's movement in the projector.

So, in essence, film perforations are tiny little holes punched into filmstrips, which help it move properly through the projector, and project an uninterrupted movie on the big screen for all of us to enjoy.