Films that need less time to record the picture are known as "faster" films. Different speeds of films are marked with an ISO number. The higher the number, the faster the films. Films can only make a picture from focused lights. If there is no lens to focus light, the film will only turn white from receiving just the light. If a film with an ISO level of 200 instead of 100 is used, it will only need half as much time to record a picture of the same scene.