A photographic film is a sheet of plastic that is specially treated to be sensitive to light when exposed and used to record pictures. A normal photographic film can hold up to 40 pictures. When all the pictures have been recorded, the film undergoes a special chemical treatment called developing or processing that makes the pictures visible to the eyes.
There are different kinds of photographic film. Some pictures don’t need too much light, while others need infrared. Some photographic films are used to take black and white pictures, while some are used to take coloured pictures.
A photographic film can be used once only once. When not in use, a film must be shielded from light. Otherwise, it will record any light that shines on it and so can no longer record any picture. So, they come in a can called canister to protect it from light rays.
A film needs the right amount of light to capture a picture. If there is the right amount of light on what is being photographed, then the picture will come out nice and bright. However, if the light is too bright or dark, then the picture will not be bright or sharp enough.
Different speeds of films are marked with an ISO number. The higher the number, the faster the films. Films can only take a picture from focused lights. If there is no lens to focus light, the film will only turn white from receiving just the light.
Examples of ISO numbers are ISO 50, ISO 100, IS0 200, ISO 400, ISO 800, and ISO 1600. When the ISO number is low, for example, ISO 100, the film takes a long time to record the picture. This is called a slow film. So, the shutter stays open for a long time.
When the ISO number is high, for example, ISO 1600, the picture is made quickly. So the shutter has to open and close quickly; this is a fast film.
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