GFA Lighting and Electric Practice Test 2026 - Free Practice Questions and Study Guide

The main idea is how light intensity changes with distance and how that affects exposure. The inverse square law says that the illumination a surface receives falls off with the square of the distance from the light source. So, as you move the light farther away, the subject gets much less light, and the image becomes darker unless you compensate. A practical rule is that doubling the distance reduces the exposure to about one quarter. That relationship directly drives exposure control: you adjust lighting, aperture, ISO, or shutter to keep the desired brightness.

Color temperature and white balance are about the color characteristics of the light, not how its brightness falls off with distance. Shutter speed does influence exposure by controlling how long the sensor collects light, but the inverse square law is specifically about how light intensity diminishes with distance, which then informs how you set exposure.