How Does Camera Film Work?

Photographic film is a medium for recording images, and up until digital cameras became popular, was the main method of doing so. In cameras, an image is captured by exposing some sort of capturing medium to light via a lens. In digital cameras, the capturing medium is a sensor, while in film cameras, it is the film itself.  

The elements of photographic film

Modern camera film is made of a thin sheet of polyester (usually with a width of 35 mm) that has been coated with layers of various chemicals like silver salts and various dyes. These chemicals react to light in such a way as to capture the image. The types of chemicals and the number of layers vary according to the type of film it is. Some types of film may have more than a dozen layers of chemicals, others as little as three.

Processing photographic film

In order for a image captured on film to be viewed, the film must undergo processing. In the case of black and white photography, photographic print is made when the captured image is projected through the film onto light-sensitive paper. When the image appears on the paper, it is washed in chemicals that remove the paper’s sensitivity to light. The image is now “fixed” on the paper and has become what is commonly called a photograph.

How film photography works

The lens in a camera focuses light on the film. This is called “exposing” the film. The chemicals on the film react to the light capturing the image of whatever the lens is pointed at. Film types differ according to the chemicals on them and how sensitive they are to light. The speed with which film reacts to light is called “film speed” and is a way for photographers to rate the sensitivity of film. When the film takes a long time to react to light, the shutter has to remain open for longer, and both the camera and the object being photographed have to remain perfectly still for the photograph to be clear.