Light Meter・Lux Meter

LUX LIGHT METER — MEASURE LIGHT LEVELS IN LUX

Lux Meter turns the rear camera into a reflected-light meter. Point it at a surface and read the level in lux or foot-candles, plus EV at ISO 100 — a desk, a bench, a houseplant in a British winter.

WHY YOU CAN TRUST THE FIGURE

▸ The metering method stays 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 stops the flicker.
▸ Over 2 seconds without a fresh frame is marked Stale; unusable metadata is marked Error.
▸ Move the target, change zoom or lens, return from the background or recalibrate: the window restarts.
▸ Nothing is saved or sampled until the reading is valid and stable.

WORKPLACE AND ROOM LIGHTING SURVEYS

Choose the space or task, then run the five-point survey: five samples across the working plane, each held until it settles, 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 theatre 1000+, bedroom 50–150, plus kitchen, bathroom, garage, shop floor and restaurant — practical guidance, not legal certification.

HOUSEPLANTS, GROW LIGHTS, PPFD AND DLI

A plant light meter only helps if it answers for the plant in front of you. Measure at the leaf plane, pick the plant, the light source and the photoperiod, and get 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, strawberry. 5 light sources: sunlight, white LED, fluorescent, HPS, metal halide. The sample log marks periods it could not cover, so a low total never reads as a full day.

EXPOSURE FOR FILM AND VIDEO

The same measurement meters an analogue camera: 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 shows the exact result, the nearest setting your kit offers and the residual error in stops — outside the 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.

HISTORY AND CSV EXPORT

Readings, surveys, DLI estimates, comparisons and monitoring share one history list — every entry keeps its method, readiness state, calibration and mode inputs. Page the archive, export to CSV.

ALSO INCLUDED

▸ Reference tables — 16 lux environments, a 0.1 lx full moon to 130,000 lx direct sun; 11 EV scenes, −6 EV starlight to +18 EV snow
▸ A/B comparison — take A, walk to B, read the EV difference and brightness ratio
▸ Continuous monitorin