Measure & Compare Softbox and Grid Light Falloff
Start with your own readings. Calculate the change, verify a frame, and save what works.
Modifier curve comparison
Record and compare measured falloff across real configurations.
Measure the modifier you actually use
Record a series of incident meter readings for two configurations. Compare raw readings and normalized curve shapes without assuming that a grid or large softbox has one universal falloff behavior.
- Keep aim, source origin, ISO, meter orientation and power consistent within a series. Record two to six distances and aperture-plus-tenths readings.
- Label the modifier, grid and diffusion configuration. Compare each curve to a clearly labeled inverse-square reference.
- Repeat measurements after changing the modifier. Distinguish normalized shape from absolute output, and verify the camera result.
A series of f/8 at four feet and f/4 at eight feet has a two-stop measured decrease. A different modifier can show a different local curve; that is a result to investigate, not a universal manufacturer specification.
Can I compare different powers as modifier loss?
No. For an output-loss comparison, keep power, distance, aim and ISO consistent. Normalizing each series compares its shape, not its total output.
Does a drawn line prove what happens between readings?
No. Connecting measured points helps you inspect a trend. Untested distances remain predictions.
By Dwayne of DNA Premium Portraits, Sacramento-area portrait photographer. See formulas, assumptions and equipment sources.
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