The film was made of celluloid before, material used for filming since the cinema was born. Now it is made of a very similar material, but this one isn't inflammable. It is impregnated by a material called emulsion which is sensitive to light and colors. Some films are more sensitive to light than others.
The films that need a little light are used to make pictures or night scenes and those which need more light are good for making scenes during the day. The films which need a little light are called very sensitive films and those which need abundant light receive the name "not very sensitive to light".
It consists of a cellulose acetate base approximately 0.006 in. thick and coated with a light-sensitive emulsion that is made in large rolls about 54 in. wide and about several thousand feet long which slits into 35-mm strips, packed, and perforated in lightproof bags and cans in rolls 100, 200, 400, and 1000 ft in length.
There are two different types of film: negative film, from which a print is made in order to see the original subject in its true likeness, and reversal film, in which a negative is first formed in the original film and from this a positive is formed in the same piece of film.
FormatsThere are many formats of films which are determined by the total width and the useful surface of each picture.