using synchronized phonograph discs (sound-on-disc), Fox placed the soundtrack in an optical record directly on the film (sound-on-film) on a strip between the sprocket holes and the image frame. "Sound-on-film" was soon adopted by the other Hollywood studios, resulting in an almost square image ratio of 0.860 in by 0.820 in. By 1929, most movie studios had revamped this format using their own house aperture plate size to try to recreate the older screen ratio of 1.33:1. Furthermore, every theater chain had their own house aperture plate size in which the picture was projected. These sizes often did not match up even between theaters and studios owned by the same company, and therefore, uneven projection practices occurred. In November 1929, the Society of Motion Picture Engineers set a standard aperture ratio of 0.800 in by 0.600 in. Known as the "1930 standard", studios which followed the suggested practice of marking their camera viewfinders for this ratio were: Paramount-Famous-Lasky, Metro-Goldwyn Mayer, United Artists, Pathe, Universal, RKO, Tiffany-Stahl, Mack Sennett, Darmour, and Educational. The Fox Studio markings were the same width but allowed .04 in more height. In 1932, in refining this ratio, the Academy of Motion Picture Arts and Sciences expanded upon this 1930 standard. The camera aperture became , and the projected image would use an aperture plate size of , yielding an aspect ratio of 1.375:1. This became known as the "Academy" ratio, named so after them. Since the 1950s the aspect ratio of some theatrically released motion picture films has been 1.85:1 (1.66:1 in Europe) or 2.35:1 (2.40:1 after 1970). The image area for "TV transmission" is slightly smaller than the full "Academy" ratio at , an aspect ratio of 1.33:1. Hence when the "Academy" ratio is referred to as having an aspect ratio of 1.33:1, it is done so mistakenly. Widescreen The commonly used anamorphic format uses a similar four-perf frame, but an anamorphic lens is used on the camera and projector to produce a wider image, today with an aspect ratio of about 2.39:1 (more commonly referred to as 2.40:1). The ratio was formerly 2.35:1—and is still often mistakenly referred to as such—until an SMPTE revision of projection standards in 1970. The image, as recorded on the negative and print, is horizontally compressed (squeezed) by a factor of 2. The unexpected success of the Cinerama widescreen process in 1952 led to a boom in film format