Light Meter・Lux Meter

LUX METER — LIGHT LEVELS IN LUX AND FOOT-CANDLES

Lux Meter is a camera-based light meter for illuminance. Aim the rear camera at a surface and read the level in lux and foot-candles, plus EV at ISO 100 — desk lighting, a grow light over houseplants, a scene for an analog camera.

WHY THE NUMBER IS WORTH TRUSTING

▸ Metering method always on screen: Reflected · Point AE or Reflected · Center.
▸ Readiness comes from a 1.2-second EV window: 6 valid samples over 650 ms within a 0.16 EV spread to lock, then a 0.28 EV hysteresis against flicker.
▸ No fresh frame for 2 seconds reads Stale; unusable metadata reads Error.
▸ Moving the target, changing zoom or lens, returning from background or recalibrating restarts the window.
▸ Nothing saves or samples until the reading is valid and stable.

ROOM AND WORKPLACE LIGHT LEVELS

Pick the space or task, then run the five-point survey: five samples across the working plane, each held until stable, giving average, minimum, target range, observed min/average uniformity and the sampling grid.

15 practical targets in 5 groups: general office 300–500 lx, detailed office work 500–750, precision factory 750–1000, warehouse and hospital ward 100–200, corridor 100–150, classroom 300–500, library 500+, operating room 1000+, bedroom 50–150, plus kitchen, bathroom, garage, retail floor and restaurant — practical guidance, never legal certification.

GROW LIGHTS, PPFD AND DLI FOR PLANTS

Measure at the leaf plane of one plant and decide for that plant: pick the plant, the light source and the photoperiod, and the reading becomes a PPFD and DLI estimate in mol/m²/day.

16 plants carry daily targets: pothos and snake plant 2–4, ZZ plant 1–3, peace lily 3–6, monstera and philodendron 4–8, fern 4–7, rubber plant 5–10, fiddle leaf fig 8–12, plus bird of paradise, succulent, herbs, tomato, pepper, lettuce and strawberry. 5 light sources: sunlight, white LED, fluorescent, HPS, metal halide. The sample log marks periods it did not cover, so a thin number never passes for a full day.

EXPOSURE FOR PHOTO AND VIDEO

The same reading solves exposure: aperture priority, shutter priority and manual across f/1.0–f/64, 1/8000 s–60 s and ISO 25–12800 in full, ½ or ⅓ stops. Each solution gives the exact result, the nearest setting your gear really has and the residual error in stops — out of range, by how many. Manual shows Over / Matched / Under on a ±3-stop scale, and Cine turns FPS, shutter angle, ISO/EI and ND into an equivalent shutter and f-number.

RECORDS AND CSV EXPORT

Readings, surveys, DLI estimates, comparisons and monitoring all land in one history list — each with its method, readiness state, calibration and mode inputs. Page the archive, export to CSV.

ALSO INSIDE

▸ Lock a reading; switch lux ↔ foot-candles in one tap
▸ Lux reference — 16 environments, 0.1 lx full moon to 130,000 lx direct sun
▸ EV reference — 11 scenes, −6 EV starlight to +18 EV snow
▸ A/B comparison — capture A, move to B, get the EV difference and brightness ratio
▸ Continuous monitoring — min / avg / max trend, real sampling interval, samples and missed samples, markers; background time logs as a gap
▸ Guided calibration — enter a reference value, aim at a uniform surface, wait for stable, apply the offset

LIMITS AND PRIVACY

A reflected-light estimate from camera exposure metadata — not an incident meter, not a PAR sensor, not a certified laboratory instrument — so it depends on the surface you aim at. The camera only measures light: no photos taken or stored, nothing uploaded, no account, and readings leave your device only in a CSV you export.

Free covers the live reading and its readiness state; Pro removes ads and unlocks every workflow.

Point, wait for stable, read the number — and stop guessing how much light really reaches that desk or that leaf.

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