Calculator
Workout the level of incident light you need (fc / lux) for a given ISO, f-stop and shutter angle. Defaults to 24 fps / 180°.
Required illuminance
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Exposure time (t)
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What’s the math?
For incident light at 24 fps with a 180° shutter, the American Cinematographer table aligns with:
where t is exposure time in seconds. For lux, multiply by 10.764.
For fps + angle:
Efc ≈ 25.5 × (N²) / (t × ISO)where t is exposure time in seconds. For lux, multiply by 10.764.
For fps + angle:
t = (angle / 360) / fps.