Film speed refers to the sensitivity of photographic film to light, measured using the ISO (International Standards Organization) scale. A higher ISO number indicates greater sensitivity, allowing for better performance in low-light conditions. Conversely, lower ISO values are ideal for bright environments, producing finer grain and higher image quality. In digital photography, film speed is analogous to the sensor's sensitivity to light. Adjusting the ISO setting on a camera can help achieve the desired exposure in various lighting situations. However, increasing the ISO can also introduce noise, affecting the overall image quality, similar to the graininess seen in high-speed film.