Flash range refers to the distance over which an electronic flash can effectively illuminate a subject. Every flash has a maximum distance it can reach, beyond which the light is too weak to produce a proper exposure, and a minimum distance, closer than which the light may be too intense and cause overexposure. The distance between these two points defines the flash range.
Flash range can be influenced by several factors, including the sensitivity of the film or digital sensor, with faster films or higher ISO CCDs extending the effective range. Diffusing the flash with neutral density filters or other materials can reduce the intensity and limit the range. Standard flash range measurements are usually based on ISO 100 film or an equivalent CCD sensitivity, though APS cameras are often referenced at ISO 200. Understanding flash range is essential for photographers to achieve correctly exposed images in both studio and low-light situations.