Flash & Ambient Balance Calculator
Start with your own readings. Calculate the change, verify a frame, and save what works.
Flash & ambient
Account for the ambient light already on your subject.
Balance flash with the ambient already on your subject
When daylight or room light contributes to the subject, doubling flash does not necessarily make the total exposure one stop brighter. This tool uses a measured flash percentage and adds the ambient and flash contributions before solving the new flash requirement.
- Measure flash percentage at the final shutter, ISO and subject point.
- Enter your total subject target and any ambient change.
- Check the ambient floor, apply the power estimate and verify the result.
If flash contributes 50% of the original subject exposure and ambient stays unchanged, a one-stop brighter total needs three times the original flash contribution, approximately +1.58 stops.
Why can the tool say my darker target is impossible?
Ambient alone may exceed the desired total. Flash cannot subtract that light; reduce ambient exposure or change the setup first.
Can I use the Sekonic flash percentage at a very fast shutter?
Use a camera-validated contribution estimate when the camera captures only part of the flash pulse. A complete-pulse meter measurement may not represent that short exposure.
Learn the decision behind the setting.
By Dwayne of DNA Premium Portraits, Sacramento-area portrait photographer. See formulas, assumptions and equipment sources.
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