Set the same value on the ASA dial on top of the camera.
Calibrate once. In full sun, meter a grey card or the clear north sky. It should read about EV 15. If it does not, swipe the offset until it does. The phone saves the value.
Photo metering: the page reads shutter, ISO and f-number from the photo, so it needs no lens setting. Use the 1× lens and switch off Live Photo and Night mode.
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