Old black and white films, such as Charlie Chaplin movies, appear to be sped up due to differences in film projection speeds between the time they were made and modern times. In the early days of film, cameras recorded at lower frame rates, usually around 16-18 frames per second (fps). However, as theaters tried to fit in more showings per night, projection speeds were increased to around 20-24 fps. As a result, when films recorded at lower frame rates are projected at higher speeds, the action appears sped up.
Additionally, economic factors also played a role in the lower frame rates of early films. Film stocks were slow and expensive, so shooting at lower frame rates was more cost-effective. Furthermore, early filmmakers also discovered that shooting at lower frame rates created a more natural-looking motion when projected at higher speeds. This was due to the persistence of vision phenomenon, where the brain retains an image for a brief period after it is no longer visible, creating the illusion of continuous motion. Therefore, shooting at lower frame rates and projecting at higher speeds was a practical and aesthetic choice for early filmmakers.