Shutter Speed from Lux

Estimate a correct shutter speed from incident illuminance (lux), aperture (f‑number) and ISO. Uses the standard incident‑meter formula: t = (N² × C) / (E × S).

Luminance — lux (lx)

ISO (S)

Aperture (N) — f‑number

Meter calibration (C)

Round to nearest standard shutter? Formula source: ISO exposure equation (see notes). Lux detection requires a browser that supports the Ambient Light Sensor API (not all phones/browsers support this).

Calculated shutter time

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Exposure Value (EV)

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Notes: uses the incident‑meter exposure equation: N²/t = E·S/C → t = (N²·C)/(E·S). C depends on meter calibration; typical flat sensor value C ≈ 250 (gives E = 2.5·2^EV at ISO100).