Why is silver iodide used in photography?

Silver iodide is used in photography because it is a light-sensitive silver halide compound. Along with silver bromide and silver chloride, silver iodide is incorporated into the emulsion of photographic films and papers.12

When these crystals are exposed to light within a camera, they undergo an invisible chemical change that creates a latent image. Specifically, light releases electrons from the silver halide crystal, which migrate to sensitivity specks on the crystal's surface. This process attracts silver ions, causing them to accumulate as metallic silver. Once these sensitivity specks reach a sufficient size, they allow a developer to chemically reduce the entire crystal to metallic silver, thereby making the image visible.1