The Top 10 Photography Lighting Facts You Should Know
The farther the light source, the more it falls off
5. The farther the light source, the more it falls off— gets dimmer on your subject. The rule says that light falls off as the square of the distance. That sounds complicated, but isn’t really. If you move a light twice as far from your subject, you end up with only one-quarter of the light on the subject.
In other words, light gets dim fast when you move it away— something to keep in mind if you’re moving your lights or your subject to change the quality of the light.
Also remember that bouncing light—even into a shiny reflector that keeps light directional— adds to the distance it travels.
Tip: Set your camera’s flash (pop-up or hot-shoe) to fill flash for outdoor portraits on harshly lit days. This will lighten shadows on your subject’s face but won’t affect the background exposure—it will fall off by then.