35mm and 15mm both refer to the same kind of chemically based photographic film used for cinematography; the difference in name results from its width. 35mm film is 35 millimeters in width while 16mm film is, of course, 16 millimeters in width. The difference in width results in significant differences both film quality and cost.
Photographic film was first created in 1892 and has changed very little since. Both movie film and still photographic film is based on the same principle of construction: photographic emulsion made up of silver halide crystals attached to a plastic strip film base. The silver halide is extremely light sensitive, so when it is exposed to light the silver ions move around and “stack” together and upon each other forming what we see as the image (but it is really just clumps of silver). The image is only visible, however, after the use of a chemical agent to release the latent image and show
In 1909, 35mm film was established as the international standard for film widths for motion pictures. However, though 35mm is the standard, there are multiple variations in width. Aside from 16mm, there also exists 8mm and 70mm. The width is the physical dimension of the film; therefore, physically an 8mm film is extremely small and a 70mm extremely fat in comparison to the standard 35mm. The price of film is directly correlated to the increase or decrease in size. For this reason, 35mm proved the best quality for the size (price).
16mm film was created for use in amateur, television and low-budget education films. 16mm is much more cost-effective than 35mm, and was first intended to allow the “everyday man” to experiment with film. Later, 16mm became a popular professional grade format for use in many television shows (even in 2010) and for artistic sequences in some motion pictures. Most 16mm film contains one perforation (little square hole on the side) per frame (whereas 35mm contains 4).
35mm, as already stated, is the standard grade film in the motion picture film industry for its high image quality for its cost. The picture produced on 35mm is sharper, of higher color quality and contains less grain than a film made on 16mm film. There is a visible difference between the films used and is usually noticeable on both large and small format screens.
Though there are huge advances in digital film technology in the motion picture film industry, many movies are still (as of 2010) shot with traditional 35mm film and many television programs (in the United States and around the world) are still shot with 16mm. The type of medium used is completely up to the preference of the cinematographer based on the desired effect.