Frequently asked questions

Android 8.0 (API 26) or later. The app uses modern Camera2 APIs that older Android versions do not support. Almost any phone made after 2018 will work.

Yes. Metering, calculation, logging, gear management, film stock data, and every calculator work entirely offline. The only optional features that use the network are weather, the ephemeris (sun and moon position), and downloading community sensor calibration profiles. You can opt out of all three.

Camera (required, used only while the viewfinder is open, to read light), Location (optional, for the ephemeris and weather), Storage (used when you export shot logs to CSV), and Notifications (optional, used by the bulb timer and reminders). The app never records video, never takes photos, and never sends camera data anywhere.

Out of the box, most phones land within roughly one stop of a Sekonic or comparable handheld. After a one-time calibration against a known reference (a grey card under steady light, or another meter you trust), most users land within one third of a stop, which is the same tolerance as the meter built into a serious film camera. The calibration is saved per device.

Start with reflected center-weighted metering: just point the phone where you want the camera to point and trust the reading. This works for the vast majority of scenes, including most portraits, street, and landscape shots. Move to spot or multi-spot only when the scene has very strong contrast or when you specifically want to control which tone falls where, like with the Zone System.

Ansel Adams built it as a way to decide in advance where a tone falls on the print. Zone 0 is the darkest black film can hold, Zone 5 is middle grey, Zone 10 is paper-base white. You take a spot reading off a shadow, another off a highlight, and figure out where they land. The exposure follows. A few rolls and it clicks. That said, you do not need it to use this app. Center-weighted metering handles most scenes without any zone thinking. If you want to go deeper, the zone placement tool is there.

Sunny 16 works fine on a flat white-wall noon-day scene. Real scenes are not that. Overcast sky? Snow? Dappled shade? Sunny 16 has no idea. The meter is looking at the actual light bouncing off the thing in front of it right now. On negative film, trust the meter and favor the shadows a little. On slide film, protect the highlights. Sunny 16 is a sanity check, not a reading.

For backlighting, point your spot at the subject's face. The bright sky behind it is irrelevant. If you meter the whole scene, you'll get a silhouette. For snow, the camera's meter tries to pull everything toward 18% grey, so it wants to underexpose badly lit snow by two stops. Either add two stops of compensation, spot-meter a shadowed patch of ground nearby, or use the spot tool on actual skin or bark. The tricky-scene guide in the app walks through each of these one step at a time.

Long exposures work fine. Set your shutter to Bulb, punch in the target time, and the built-in timer handles the countdown with a haptic tap and an optional voice cue, so you are not squinting at the screen in the dark. The trickier part is reciprocity failure. Pick your film stock and the app works out the corrected time for you. On HP5 at ten minutes that correction can nearly double the recommended exposure.

Yes. The app ships with a large database of common cameras, lenses, and film stocks, and you can add your own with custom shutter ranges, aperture ranges, flash sync speeds, and bellows extension factors. Custom gear is saved locally and can be exported.

Add it. The film stock screen lets you create a new stock with custom ISO, latitude, reciprocity curve, push and pull development times, and notes. You can copy from an existing stock and then tweak, which is faster than starting from scratch.

Yes to both, automatically. Tell it which filter is on the lens (red, polarizer, ND, IR, etc.) and it subtracts the filter factor from the recommended exposure. For long exposures, it applies the right reciprocity curve for the loaded film stock. Bellows extension on large format is supported too.

Yes. There is a per-roll setting for how many years past the expiration date the film is, and the app adjusts the recommended exposure based on the standard one-stop-per-decade rule, which you can override per stock if you know your specific film behaves differently.

No. The app has no analytics, no telemetry, no third-party SDKs, no advertising identifiers, and no account system. Everything stays on your phone. The full privacy story is on the privacy page.

Everything is in a local SQLite database on the phone. You can export your shot logs and rolls to CSV at any time from the Logs tab. The CSV opens in any spreadsheet tool and includes a Lightroom-compatible metadata preset.

Yes, unless you exported first. There is no cloud sync to fall back on. This is on purpose, to keep the app local-first, but it means you should export your roll logs occasionally if they matter to you. A two-tap CSV export is built in.

An iOS port is in early development. The Android version is the focus today and has the full feature set. When iOS ships, per-feature pages on this site will note any differences.

Email hello@zonelightmeter.com with what you expected, what happened, your phone model, and Android version. Screenshots help. The developer reads every message personally.

There is no fixed schedule. Updates ship when features are ready, usually every few weeks. Every shipped feature gets a documentation page on this site at the same time, so if it works in your hands it is also documented here.