Silent films were shot at a 1.3 aspect ratio (also known as a 4:3 aspect ratio), with each frame using all of the negative space between the two rows of film perforations for a length of 4 perforations. The frame line between the silent film frames was very thin. When sound-on-film was introduced in the late 1920s, the soundtrack was recorded in a stripe running just inside one set of the perforations and cut into the 1.33 image. This made the image area "taller", usually around 1.19, which was slightly disorienting to audiences used to the 1.3 frame and also presented problems for exhibitors with fixed-size screens and stationary projectors.