Because the light created by a flash moves away from the flash source it appears to disappear; for instance, the light from a single flash illuminates a subject 20 feet away slightly, 10 feet adequately, and 5 feet too brightly. This is known as:

Question

Quizplus · Accepted Answer

The described phenomenon is a result of the Inverse Square Law, which states that light intensity decreases as the distance from the source increases. Specifically, the intensity of the light is inversely proportional to the square of the distance from the source. Therefore, the subject closer to the flash appears brighter, while the subject farther away is less illuminated.

Because the Light Created by a Flash Moves Away from the Flash