Pupila
Pupila Support
Updated September 26, 2026
Answers to common questions about Pupila, the light meter for iPhone and iPad. Can't find what you need? Email support@apphunt.app.
Getting started
Open Pupila and allow the camera when iOS asks: light is measured from the live image. The Light tab shows illuminance in lux (tap lux in the corner for foot-candles). Tap the pause button to hold a reading, and the arrow to reset minimum, average and maximum.
Measuring light
Facing up: lay the phone flat where you want to measure, screen towards the light, like a real lux meter. Keep your head and hands out of the way.
White paper: the most reliable method. Put a sheet of white paper where you want to measure and point the back camera at it so it fills the view.
Scene: a quick estimate from the back camera, assuming an average scene.
Phone cameras aren't calibrated instruments, so readings are estimates. To match a lux meter, measure the same spot with both, then enter the meter's value in Tools → Calibration. The front and back cameras keep their own offsets, and the meters use them automatically.
Exposure for film and digital
In the Exposure tab, set your film speed or camera ISO on the ISO dial. In aperture priority you pick the f-number and Pupila shows the shutter speed; drag the shutter dial to switch to shutter priority. Tap anywhere in the viewfinder to spot meter that area, tap Spot to go back to average metering, and use the lock to keep a reading while you set your camera. Choose full, half or third stops with the slider button.
Meters see the world as middle grey. For snow, a white wall or a bright beach add +1 to +2 EV of compensation; for a dark subject take some away.
ND filters and long exposures (Premium)
Pick your ND filter and Pupila adds its stops to the calculation. Pick your film stock and, for exposures over one second, Pupila shows the corrected time from the film maker's reciprocity data (Ilford, Kentmere, Kodak Tri-X and T-Max, Fujifilm Acros II).
Plant light (Premium)
Choose your light source and your kind of plant, hold the phone at leaf height and set how many hours a day the spot gets that light. Pupila shows PPFD (the light plants use, in µmol/m²/s) and the daily light integral (DLI, in mol/m²/day) and tells you whether the spot is too dark, right or too bright. Conversion factors are typical values; purple red-and-blue grow lights can't be measured reliably with a camera, so use the numbers from the lamp's maker instead.
Color, flicker and golden hour
Color temperature: point the camera at a sheet of white paper lit only by the light you want to measure. Pupila shows Kelvin, tint and mired, and the CTO or CTB gel that brings it to daylight or tungsten.
Flicker test (Premium): point the camera at the lamp or at a white wall lit only by it and tap Test this light. Stripes in the picture during the test mean the light pulses. Under about 4 % is considered free of visible effects.
Golden hour: allow your location once and Pupila shows blue hour, sunrise, golden hour, solar noon and sunset for today and tomorrow. Add the Golden hour widget to your Home Screen or Lock Screen.
Siri and widgets
Say “Measure light with Pupila”, “Meter exposure with Pupila”, “Check plant light with Pupila” or “When is golden hour in Pupila”. For the golden-hour answer, open Golden hour in Pupila once so it knows where you are.
The Golden hour widget shows the next golden hour and today's sunset. The Light meter widget opens the meter from the Lock Screen.
Pupila Premium
Pupila is free to download. The light meter, the exposure meter with spot metering, color temperature and golden hour are free with no limits. Pupila Premium adds plant light, the flicker test, film tools and saved readings with CSV export.
Saved readings
Tap the save button on any meter to keep a reading, then find it in Tools → Saved readings. Swipe a reading to delete it, or export them all as a CSV file for a spreadsheet.
Restore a purchase
On a new device or after reinstalling Pupila, tap Restore purchases in Settings or on the Premium screen, using the Apple Account you bought Premium with.
Cancel a subscription
Apple manages subscriptions. On your iPhone, open Settings, tap your name, then Subscriptions → Pupila, and tap Cancel Subscription. Cancel at least a day before your subscription renews or your free trial ends to avoid being charged. Deleting the app doesn't cancel a subscription. For a refund, contact Apple at reportaproblem.apple.com.
Troubleshooting
Black viewfinder or no reading: allow the camera in Settings → Pupila.
“Too bright for the camera” or “Too dark for the camera”: the scene is outside what the camera can expose. Measure in shade, or add light.
Numbers jump around: hold the phone still for a second; use the hold button to freeze a reading.
No golden hour times: allow location for Pupila in Settings, or open Golden hour once with location on.
Contact
Email support@apphunt.app. Please include your device model and iOS version.