Question: How does film work? What makes it capture the shot?

Chris Armstrong answered on 24 Jun 2015:

I can’t remember the exact compounds that are used but film is essentially a thin layer of a photosensitive material that responds to visible light.

When you open then shutter light is able to hit this material, now theres countless active particles in the film so the details we see are a build up of active particles in a certain area, if a lot of light is directed in a certain area on the film more of them will be activated than an area with less light producing the image you see.

Colour film uses the same trick, but has more layers that are active to certain parts of the visible spectrum.