Lighting Ratio & Multi-Light Exposure Calculator
Start with your own readings. Calculate the change, verify a frame, and save what works.
Multi-light balance
Combine readings, design contributions, or preserve ratios.
Design key and fill contributions toward a target f-stop
This lighting ratio calculator adds measured light in linear units. It can combine isolated readings, distribute a target total between lights, or preserve current power ratios when you change aperture.
- Take individual readings at the same point, ISO and meter orientation.
- Choose combined exposure, contribution design, or ratio preservation.
- Meter the actual combination after applying the settings.
Two equal f/5.6 contributions measured at the same point combine to approximately f/8. A fill contribution one stop below the key contributes half as much light as the key at that point.
Is key-to-fill power ratio the same as facial contrast?
No. Light placement, fill spill, subject shape and surface reflectance determine the highlight-to-shadow result. Nominal power settings also cannot be compared across different flashes without measurements.
Can it tell me what power to set each flash?
The design mode uses each light’s actual reference power and isolated reading to suggest a power for its target contribution. Impossible power targets are flagged.
Learn the decision behind the setting.
By Dwayne of DNA Premium Portraits, Sacramento-area portrait photographer. See formulas, assumptions and equipment sources.
Want help turning this plan into a photograph?
Bring this lighting goal to a private Sacramento workshop. Three hours, your equipment, one focused learning plan.