Visual Light Placement & Falloff Calculator
Start with your own readings. Calculate the change, verify a frame, and save what works.
Visual light placement
Map stop distances, solve backdrop targets, and plan group evenness.
Plan the placement, then measure the result
This visual light placement calculator maps where illumination reaches a chosen drop relative to a reference point. Use separate modes for backdrop targets, group evenness, moving a light and comparing face or body points. It models distance-related illumination, not the final tone of skin, clothing or a background.
- Select a goal and enter consistent straight-line distances from the effective source. Change units to convert all distances together.
- Drag the reference points in the falloff map, or solve a target. Check room limits, flash power headroom and apparent source size.
- Meter the proposed setup with other lights off, verify a camera frame, and save the plan with your test notes.
For a backdrop three feet beyond the subject and a two-stop illumination drop, the aligned point-source model places the light three feet from the subject and six feet from the backdrop. A four-foot-deep group needs about 21.14 feet from light to front row to keep distance-related variation within half a stop.
Where does light falloff start?
Illumination decreases continuously as distance increases. The half-, one-, two- and three-stop markers are thresholds relative to point A, not boundaries where light suddenly begins to fall off.
Can I get perfectly uniform group lighting just by increasing distance?
For a positive group depth, zero distance-related difference has no finite solution in this model. Choose a practical tolerance, reduce the group depth, or use feathering and additional light verified by readings.
Can this guarantee a two-stop difference across a face?
No. The face/body comparison only estimates the contribution from each point’s distance to the light. Surface angle, facial shadows, beam shape and reflected fill also matter. Use consistent isolated meter readings to establish the actual relationship.
Does inverse-square math work with a close softbox or grid?
It is a starting estimate. A nearby extended source, feathering, beam edges and bounce can depart from it. The measured-falloff tool compares your actual readings and checks a third point.
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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