What is the primary role of developer chemicals in film processing?

The primary role of developer chemicals in film processing is to create a visible image from the latent image. When photographic film is exposed to light, it captures a latent image that is not immediately visible. The developer chemicals react with the exposed silver halide crystals in the film emulsion, reducing them to metallic silver, which forms the dark areas of the image. This chemical reaction is essential for revealing the latent image, making it visible.

The other options, while related to aspects of film processing, do not accurately describe the main function of developer chemicals. Fixing the image refers to the role of fixing agents that stop further development and make the image permanent. Enhancing film speed pertains to characteristics of the film and its sensitivity to light, which is not directly affected by the developer. Prolonging the shelf life of the film is related to storage conditions and the chemistry of the film itself, rather than the function of developer chemicals during processing.