What is photographic film made from?

Film is composed by two main parts, the base and the emulsion.

The base is where the emulsion lies. Usually it’s made of cellulose triacetate, acetate, or polyester. It’s a synthetic support that holds the emulsion.

It’s designed to endure winding and re-winding in the camera, so the most important characteristic is its ability to stretch, while maintaining a clean and uniform transparency. It must be resistant to scratches (as much as possible, camera functionality matters) and protect the emulsion, while also allowing the emulsion to be active.

Most film bases are made from plastic pellets that are melted and then stretched to a flat surface and cooled until the desired final size is reached.

The emulsion is the active ingredient that will capture the final image. When at its solid sate the emulsion consists of light-sensitive particles dispersed onto a gelatin support, and then coated on the base.

Built up from multiple layers of dyed silver halides, the emulsion, when hit by light, will transform into a latent image. Each layer will capture the correct corresponding wavelengths of the color spectrum.

Other important layers that are part of the film composition are positioned at the top, in between, and at the bottom, to control UV light, and anti-halation.

Photo credit: disasterarea

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