There are five commonly used formats (gauges) of film stock. Each has defining characteristics that makes differentiating between them a relatively simple task.
The primary difference between four of the gauges is their physical width in millimetres and, to make things even simpler, they are known by those widths. e.g. 9.5 mm film is so called because it is 9.5 millimetres wide. You can therefore measure the width of your footage to ascertain the gauge, in most cases. The only exception to this easy to use definition is 8mm film, as there are two film gauges of this width.
The Five Gauges
Introduced in 1932 by Eastman Kodak, standard 8 mm film was aimed at the amateur film maker but designed to be cheaper than 16 mm. Like its successor, Super 8, it is 8 mm wide. The way to differentiate between the two is by the size of the perforations or sprocket holes, which are used to pull the film through the projector and camera. Standard 8 mm film was made from 16 mm film and therefore has the same size perforations as 16 mm, each one being situated at the line between the frames.
In 1965 Eastman Kodak released super 8 mm film, which, like standard 8 mm is 8 mm wide. The way to differentiate between the two is the size of the sprocket holes. The aim of producing super 8 was to increase the size of the picture area and thereby improve the quality of the projected image. This was achieved by reducing the size of the perforations or sprocket holes, which are used to pull the film through the projector and camera. Unlike standard 8 mm film the perforations are situated at the cente of the frame rather than between them.
Pathé Frères introduced 9.5 mm film in 1922 as a way of selling commercially made films to home users, although a simple camera for amateur film makers was produced soon after. It is easily identifiable as it is not only 9.5 mm wide but also has centrally situated rectangular perforations or sprocket holes, which are used to pull the film through the projector and camera, between each pair of frames.
16 mm film was introduced by Eastman Kodak in 1923 as an inexpensive amateur alternative to 35mm. However, by the 1930s it was being used extensively by professional production companies.
It is 16 mm wide and the perforations or spocket holes, which are used to pull the film through the projector and camera, can either appear on both edges of the film or along one edge.
This film gauge has been used since the early days of cinema and was the unquestioned choice of professional film makers throughout the twentieth century. It is only in recent years that the industry has started to consider replacing it with digital technology.
The appearance of 35mm stock has changed little over the last one hundred years. The perforations or sprocket holes, which run along both edges of the film and are used to pull the film through the projector and camera, were standardised at the beginning of the twentieth century. Before this standardisation the shape and frequency of the sprocket holes varied depending on the producer. Consequently, it is sometimes possible to determine who shot a piece of film from the early period of cinema by simply looking at the sprocket holes. MACE can help you with this process of identification if it is necessary.
Up until 1951 nearly all 35mm film was made of cellulose nitrate when it was replaced by 'safety film' (cellulose triacetate). Cellulose nitrate, also known as nitrate film, is highly inflammable and once it is alight it gives off a poisonous gas and is very difficult to extinguish. Because of its combustibility nitrate film should be treated with caution. The Health and Safety Executive has issued a leaflet called The Dangers of Cellulose Nitrate Film.