What is the function of a processing solution's developer?

The function of a processing solution's developer is to convert exposed silver halide crystals into visible metallic silver. During the film development process, exposed areas of the film contain silver halide crystals that have reacted to radiation. The developer acts chemically on these exposed crystals, reducing them to metallic silver, which creates the black areas of the radiograph. This transformation is a key step in developing an image, as it is the process that ultimately makes the latent image visible.

In photographic terms, this process is crucial because it is what allows the detailed image captured on the film to become apparent after processing. Once this change occurs, further steps in the development process can take place, such as fixing the image to preserve it from further exposure. The developer is integral to the imaging process, as it forms the basis of how the photograph or radiograph is rendered visibly.