How does the speed of film affect grain visibility?

The speed of film significantly affects grain visibility, and faster films typically exhibit more visible grain. Film speed is determined by the film's sensitivity to light, with higher speed films (rated at higher ISO numbers) designed to capture images in lower light situations. However, this increased sensitivity often comes at the cost of grain structure.

Faster films require larger silver halide crystals to respond to light more efficiently, which results in a coarser grain structure. Consequently, when images taken on faster films are enlarged, the grain becomes more pronounced, leading to a grittier appearance. This is an important consideration for photographers, as it can influence the aesthetic of the photographs they produce, especially in genres where fine detail and smooth tonality are desired.

In contrast, slower films have smaller grains, which contribute to finer detail and smoother image quality but may struggle in low-light conditions. The choice of film speed should thus be made with an understanding of its impact on grain structure, given that visible grain can enhance or detract from the final image quality depending on the photographer's intent.