Tech Tools / Calculator
Photometric & Footcandle Check
Convert candela, distance and incidence angle into lux and footcandles—or solve for intensity or throw.
Planning aid only. Point-source inverse-square approximation. Ignores atmospheric loss, optics changes, reflections and near-field effects. Verify equipment specifications and on-site conditions before the show.
Setup
Results
How to use this tool
Use intensity in the direction of the target—not necessarily the fixture’s peak on-axis value. Measure the slant distance and the angle between the incoming light and the surface normal.
E(lux) = I(cd) cos(α) / d(m)². I = Ed²/cos(α); d = √(I cos(α)/E). One footcandle = 10.7639104 lux. At 10,000 cd and 10 m on axis, E = 100 lux = 9.2903 fc.
FAQ
Does this include off-axis fixture falloff?
No. Enter the candela at the actual off-axis direction from a polar plot. The cosine here only accounts for the receiving surface’s orientation.
Can I enter lumens instead?
Not without the fixture’s intensity distribution. Lumens and candela are not interchangeable.
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