Lux Meter – Light Meter

Lux Meter turns your iPhone into a professional light meter. Using your camera and the ISO 2720 photographic standard, it measures illuminance in lux and foot-candles in real time — accurately, fully offline, with no ads and no sign-up.

Whether you're setting up studio lighting, checking your desk for eye comfort, dialing in grow lights for plants, or metering a film scene, Lux Meter gives you the numbers the pros rely on.

MEASURE
• Real-time lux and foot-candle readout (tap to switch units)
• Exposure Value (EV) at your chosen ISO
• Color temperature (CCT in Kelvin) estimate from the camera
• Live camera preview with a center spot reticle
• Spot metering (center) or average metering (whole frame)
• Min / max / average statistics with a live chart
• Hold to lock a reading
• Plain-language light labels (Office lighting, Overcast day, Direct sunlight…)
• Low-light path reads down to sub-1 lux

EXPOSURE CALCULATOR (2-in-1)
• Set any two of aperture / shutter / ISO — it solves the third
• Cinema mode: frame-rate and shutter-angle presets, plus the 180° rule
• ND filter and exposure compensation
• Sunny 16 helper and a depth-of-field estimate

TARGETS & PRESETS
• Use-case presets: Reading, Office/Ergonomics, Photography, Film/Video, Plants & Greenhouse, Aquarium/Terrarium
• Set a target lux band and get a subtle alert when the light is in range
• Optional haptic and audio meter tick that speeds up as light increases

CALIBRATION YOU CAN TRUST
• Independent calibration for front and back cameras
• Multi-point calibration fitted across the whole range
• See raw and calibrated values side by side
• Reset to default anytime

SAVE & EXPORT
• Save single readings or record a session over time
• Min/max/average per session, notes and optional location tag
• History list with rename, delete and CSV export (share sheet)

BUILT RIGHT
• Works 100% offline — no account, no tracking, no network
• No ads, nothing locked behind a paywall
• Grid and histogram overlays, screen-brightness pin, keep-awake
• Clean dark-first design, light mode too
• 8 languages with instant in-app switching

A note on accuracy: iOS does not give apps access to the ambient light sensor, so Lux Meter uses camera-based reflective metering (ISO 2720). For best results, calibrate once against a reference and use the same lighting conditio