Flash Exposure & Background Planner
Start with your own readings. Calculate the change, verify a frame, and save what works.
Exposure & background
Set a brightness goal for your subject and background.
Plan separate subject and background exposure changes
This flash exposure planner starts with a photograph that already gives you a useful baseline. Tell it how many stops brighter or darker you want the subject and background, then choose whether the background is lit by ambient light, a separate flash, or the same flash.
- Enter your current shutter, aperture, ISO and flash powers.
- Set a subject and background change in stops, and account for ambient reaching the subject.
- Apply the starting plan, meter each contribution and verify a camera frame.
With a flash-only subject at 1/32 and an ambient-only background at 1/250 s, a +1 stop subject and −2 stop background target suggests 1/16 power and 1/1000 s if the full flash pulse is still captured. Very fast shutter speeds require testing.
Can I make the face brighter and the dress darker with one light?
A power change affects every region receiving that light. Use the spill mapper with measurements at each region, or change placement, feathering or flags.
Does faster shutter always leave flash exposure unchanged?
Only when the captured flash energy is unchanged. On the Sony a9 III, a short exposure can capture only part of the pulse, so timing and brightness must be retested.
By Dwayne of DNA Premium Portraits, Sacramento-area portrait photographer. See formulas, assumptions and equipment sources.
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