Film Speed F ilm comes in all types both black and white and color and in all sizes from the tiny 110 to the large 220. For our class at Santa Cruz High School we work only with black and white film which is 35 mm in size. This is the main division between types of films.
Speed is how fast a film can capture an image when exposed to a minimal amount of light.
This speed is given a calibration number so that we can compare films with each other. This number is called ASA which stands for American Standards Association or it can be called ISO which is the same number but represented by the International Standard Organization. These numbers can be from 1 to up over 32,000. The actual scientific process for determining that number is more than we need to know, it will suffice to say that the smaller the number the slower the film and the longer it will take to make an exposure. This is film with an ASA of less than 100.