Volume Button Triggers
VOLUME_DOWN measures, VOLUME_UP toggles lock. So you can meter without looking at the screen.
Where to find it
Viewfinder (system-wide physical buttons)
Summary
Volume buttons are remapped for hands-free metering. Press VOLUME_DOWN to measure light (same as tapping the meter button). Press VOLUME_UP to toggle exposure lock. In zoom mode, the same buttons control zoom. Prevents accidental volume changes.
How it works
How to use it
Point your phone at a scene, press the physical VOLUME_DOWN button on the side of your phone. That is the same as tapping the big red Measure Light button on the screen. The meter takes a reading and freezes the preview. You do not have to touch the screen.
Locking exposure
Press VOLUME_UP to toggle the exposure lock. Locked exposure stays frozen even if you move the phone or the scene changes lighting. Press VOLUME_UP again to unlock and meter live.
Switching to zoom mode
Long-press the meter button to enter zoom mode (or pinch on the preview). While zoomed, VOLUME_UP and VOLUME_DOWN control zoom level instead of metering. Tap the screen to exit zoom and return to metering mode.
Why this matters
Film photographers often hold the camera with both hands or have a light meter in one hand. Physical buttons let you work without putting the phone down or rearranging your grip. It is one of the easiest ways to work hands-free in the field.