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★★★★★
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• New app icon: the same picture as on the store page – a large white-and-amber sun with thin rays on a warm black tile, edge to edge. Before, a smaller sun sat inside a dark frame. • The start screen uses it too. Meter, History and your saved readings stay as they were.
Measure light properly — in lux, foot-candles, EV, or PPFD for plants — using your iPhone's camera to read the light falling on the scene. GROW LIGHTS & PLANTS • PPFD estimated from your live reading, matched to your light source: white LED, HPS, fluorescent or daylight • DLI for a 12, 14, 16 or 18 hour photoperiod, so you can tell whether a shelf actually reaches a seedling's daily light target • These are spectrum-based estimates, not a calibrated PAR sensor. Read them as guidance for placing lights, not as lab data. FOUR MEASURING MODES • Auto — radial gauge with the closest real-world reference shown live • Outdoor — a log scale to 100,000 lx, from deep twilight through overcast and direct sun • Indoor — 10 to 10,000 lx, from corridor and living room up to reading desk, drafting and surgical levels • Photo — EV at ISO 100 with a suggested shutter speed HISTORY THAT ADDS UP • Every reading saves automatically, with a 7-day trend chart and plain-language insight such as "+12% vs your 7-day average" • Notes and favourites — label a reading "kitchen window 3pm" and star it • Compare any two saved readings side by side • Export everything as CSV, or share a single reading as an image MEASUREMENT DETAIL • Kalman-smoothed readings, so there is no jitter to read through • Min, max and average with elapsed time • Log-scale range bar in Outdoor and Indoor modes • Lux, foot-candle and EV units • Calibration factor — scale every reading by a multiplier to match a reference meter you trust WHO USES IT Indoor gardeners and grow-tent owners · photographers and filmmakers · electricians and lighting installers · studio engineers · workplace and office ergonomics checks · industrial lighting surveys HOW IT WORKS Readings are estimated from the back camera's exposure, so this is a reflected-light measurement: point the back of the phone at the surface you care about and keep the lens clean and unshaded. Because it reads reflected light, a white wall and a dark carpet under identical lighting will not read the same, and very dim scenes are the least reliable. Cameras differ between models, so for absolute numbers set the calibration factor against a meter you trust. Available in 25 languages.