135 working principle of traditional film camera

Film cameras mainly apply optical principles and photochemical principles.

Transparent film is coated with silver salt, silver bromide, etc. This compound decomposes when exposed to light, and the lens is imaged on the film, resulting in different decomposition depths under different light intensities. Wash away the undecomposed silver salt with liquid medicine, and the precipitated silver is black, which is fixed and dried to form a negative. Ordinary negatives are the reverse of photos, so they are also called negatives. After the same silver salt is projected on photographic paper, the image is reversed and washed with fixing solution, which is the "developed" photo as the saying goes. Drying and pruning can be stored.