Light Falloff
The rate at which illumination decreases with distance from the source, across the subject or into the background.
Formula / rule
E ∝ 1 / d²
Measured in
stops (EV)
In depth
Falloff is the reason a light's distance matters as much as its power. Close in, the difference in distance between a subject's nose and their ear is a significant fraction of the total, so the light drops off visibly across the face. Far back, that same difference is negligible and the light renders flat and even.
Examples in practice
Moving a key from 1 m to 3 m turns a face with dramatic side-to-side falloff into one lit almost evenly.