What Is the Difference Between 35mm & 70mm Film?

Filmmakers and cinematographers use a variety of advanced imaging and lighting technology to produce feature films and documentaries. Although digital filmmaking has become common, film cameras are still used for the special visual characteristics of differing film gauges. The 35 mm and 70 mm film gauges each produce unique images.

The most widely used film for still imagery and film production is 35 mm. Prior to its recognition as the international standard film gauge in 1909, cinemas used film ranging in width from 13 mm to 75 mm. Unlike 70 mm film, 35 mm film can be used in the majority of theaters around the world Over the last 100 years, the film strip has been redesigned to incorporate sound and color. This film sizehas been designed to create a 1.37-to-1 visual aspect ratio -- that is, the relationship between the film's width and height.

The 70 mm film size is often associated with IMAX and Ultra Panavision films. The 70 mm film uses a larger aspect ratio than 35 mm film, allowing for a much wider display field commonly seen in IMAX and IMAX 3D. The 70 mm film features a high-resolution image that allows for increased image clarity at larger projected screen sizes.

Although 70 mm was used infrequently in the closing years of the 20th century, developments in IMAX three-dimensional film production have brought about an increased demand for the product. As 35 mm film requires less expensive technology to project and record the imagery, the majority of cinemas and production houses continue to use 35 mm film.

The larger aspect ratio of 70 mm film allows theaters to project movies using the film on large screens without a visible loss of clarity. Movies originally filmed with 35 mm film are often converted to 70 mm for IMAX productions and drive-in theaters. One marked disadvantage of 70 mm film is the inability to encode digital sound formats such as Dolby Digital directly onto the film.