Movie cameras / video cameras are used to film movies. Movie cameras take pictures very quickly, and they usually take 24 or 25 pictures, or frames every second. When a movie projector, a computer, or a television shows the pictures at 24 frames a second, it looks like the things shown in the set of pictures are moving. Sound is usually recorded at the same time as the pictures are, but sometimes they are added later. The sounds in a movie are usually people talking, the soundtrack, and sound effects. In the 20th century the camera used photographic films.