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Summary of the steps of the traditional film photography

Film

The unexposed film is covered with colorless crystals of silver bromide $Ag^+Br^-$. This is the photosensitive layer.

Exposure

Light, impurities and sensitizers cause the formation of barely visible germs of metallic silver $Ag$ . This is the latent image.

Development (darkroom)

- The developer bath (eg hydroquinone) causes the formation of metallic visible silver grains $Ag$ . An excess of bromide (eg sodium bromide) prevents the occurrence of a veil. The layer remains photosensitive. - A stop bath (eg acetic acid) blocks the developer. The layer is still photosensitive.

- A fixing bath (eg sodium thiosulfate) dissolves the excess silver bromide. The layer is no more photosensitive.

- A wash removes soluble salts

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