Negative pulldown

2-perf, used in Techniscope in the 1960s, is enjoying a slight resurgence due to the birth of digital intermediate techniques eliminating the need for optical lab work.

4-perf was (and remains) the traditional system, and the majority of projectors are based on 4-perf, because 4 perforations is the amount needed per frame vertically in order to have enough negative space for a roughly squarish image, which became the silent film standard aspect ratio of 1.33:1.

Later, when the film industry was facing the perceived threat of obsolescence to television, universally a 1.33:1 aspect ratio at the time (and remained so in many countries until the introduction of DTV), studios started experimenting with various competing widescreen formats.

Eventually, aspect ratios of 1.85:1 in North America and 1.66:1 in Europe became standard for 35 mm productions shot with normal non-anamorphic lenses.

In the early 1980s, Swedish cinematographer Rune Ericson collaborated with Panavision on the concept of creating a 3-perf mechanism for motion picture cameras.

[2] The 3-perf system, achieved by altering the camera gate and shutter mechanism, reduces film wastage by using frames that are 3 perforations high instead of the standard 4-perforations.

In the late 1990s, cinematographer Vittorio Storaro proposed a film standard known as Univisium (also called Univision), which advocated for 3-perf Super 35 to create a 2.00:1 aspect ratio.

Paramount did not use anamorphic processes such as CinemaScope but refined the quality of their flat widescreen system by orienting the 35 mm negative horizontally in the camera gate and shooting onto a larger area, which yielded a finer-grained projection print.