How did photographic film evolve and work?

Photographic film consists of a transparent base coated with a gelatin emulsion containing light-sensitive silver halide crystals. A short exposure to light creates an invisible latent image that is chemically developed into a visible photograph. Over time, innovations like sensitizing dyes and multi-layered emulsions expanded film sensitivity from simple blue light to all visible colors.

What we know

• Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. [2]
• Unmodified silver halide crystals are sensitive only to blue light, but sensitizing dyes were discovered to make films respond to green and all other visible colors. [2]
• Color film incorporates at least three sensitive layers using different combinations of sensitizing dyes to record blue, green, and red images. [2]
• Before digital photography, film had to be chemically developed to produce negatives or projectable slides. [2, 5]

Where to go next

• what caused itHow are camera lenses designed?
• compared withWhat is digital photography?
• how it workedHow do silver halide crystals capture light?
• a case in pointWhat films are still available today?
• the bigger pictureWhat is photography as a medium?
• an unexpected connectionHow did camera obscura optics influence modern cameras?The problems of covering a large, flat image plane were well understood from camera obscura development even before the invention of modern photography.

Sources

• [1]photographic film (Wikidata Q6293) · CC0 1.0
• [2]Photographic film · CC BY-SA 4.0
• [3]List of photographic films · CC BY-SA 4.0
• [4]History of photographic lens design · CC BY-SA 4.0
• [5]Photography · CC BY-SA 4.0