Light Meter

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Metering

How do I use it with my film camera?
Set the ISO to your film's speed. Tap the side you want to set (aperture or shutter speed) and turn its dial; the other side shows what the meter suggests. Point the phone where your camera points, from where you stand. Tap Hold to keep a reading while you set the camera.

What is EV?
Exposure value at ISO 100: one number for how bright the scene is. Full sun is about EV 15, an overcast day about EV 12, a bright room about EV 8, a dim room about EV 5.

Average or spot?
Average is the camera's own center-weighted reading of the scene, like most camera meters. Spot (Pro) meters the area in the circle: tap a face, a sky or a shadow to meter just that part.

My reading doesn't match my camera or handheld meter.
Phones differ a little. Open Settings, Calibrate, meter the same evenly lit scene with both, and type the EV your meter shows (or use the Sunny 16 check in full midday sun). The offset is saved and added to every reading.

What do Full, ½ and ⅓ mean?
The steps on your camera's dials. Full stops suit most older shutter dials; many lenses click in half stops; newer cameras use thirds (Pro). With a camera preset (Pro) the meter follows that camera's marks and range.

It says "too dark" or "too bright".
The phone camera has a range too. In very dim light the true scene is darker than shown; in very bright light, brighter. The result also warns when the shutter speed or aperture you need is outside the dial (for example faster than 1/8000): close down, add an ND filter, or change the film speed.

Long exposures and reciprocity (Pro).
Past about a second, film needs more exposure than the meter says. Pick your film in Film & camera: for films whose maker publishes a formula (Ilford and Kentmere), the app shows the corrected time. For others, add your own film in Settings with the exponent from its datasheet.

Lux and grow lights

How do I measure lux?
On the Lux tab, lay a sheet of plain white printer paper where the leaves are, facing the light, and point the back camera at it from about 15 cm (6 in) so the paper fills the frame without the phone's shadow on it. On many Android phones you can also use the light sensor near the top of the screen.

What are PPFD and DLI? (Pro)
PPFD is the light plants use for photosynthesis, in µmol/m²/s; DLI is the total over a day. The app estimates both from lux using typical factors for each kind of light (sunlight, white LEDs, fluorescent, HPS, metal halide). Red and blue (purple) grow lights can't be measured in lux; use a quantum meter for those.

Pro, purchases and the camera

I bought Pro but it isn't unlocked.
Open Settings and tap Restore purchases, signed in with the Apple ID or Google account you paid with.

How do I cancel a subscription or get a refund?
Subscriptions and refunds go through Apple or Google. On iPhone: Settings, your name, Subscriptions; refunds at reportaproblem.apple.com. On Android: Play Store, your profile, Payments and subscriptions; see Google Play's refund help.

The meter says the camera is off.
Light Meter needs camera access to measure light. On iPhone: Settings, Light Meter, Camera. On Android: Settings, Apps, Light Meter, Permissions, Camera. Nothing from the camera is saved or sent (see the privacy policy).