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Lighting ratio calculator
Balance key and fill light in stops or by distance, see the classic portrait ratio you land on, and how much of the light on your subject is fill.
All tools- Lighting ratio
- 4:1Classic portrait depth: shadow side still holds detail. Nearest classic ratio: 4:1.
- Difference
- 2 stops
- Fill share
- 20%Of all the light reaching the subject
How it works
The method behind the numbers.
The lighting ratio compares the light the key puts on the subject with the light the fill puts there. Each stop of difference doubles the ratio: 1 stop is 2:1, two stops is 4:1, three is 8:1. It describes the shadow depth on a face more directly than either light's power setting.
ratio = 2^(stops)
stops = log2(ratio)
ratio = (fill distance ÷ key distance)² (equal lights)- By stops. Meter the lit side, then the shadow side, with the fill light on and the key off (or blocked); the difference is the slider's value.
- By distance. With two identical lights, brightness falls with the square of distance, so the ratio follows from where the stands sit — move the fill 1.4× further for 4:1. Modifiers and power settings break the equality, so this is the planning estimate; the meter settles it.
- Reading it. 2:1 is soft and even, 4:1 is the classic portrait depth with shadow detail intact, and 8:1 and beyond run dramatic to low-key. Fill light also lifts the whole exposure: the fill share is how much of the total light on the subject it carries.