Lighting ratio
Verlichtingsverhouding · Light
The brightness ratio between the key light and the fill light.
A ratio of 1:1 gives flat, even light. 2:1 gives subtle shadow play. 4:1 gives clear contrast. 8:1 or more gives dramatic low-key light. The lighting ratio determines the mood of a portrait: soft and approachable versus harsh and dramatic.
Tools that help with this: