iPhone Duo Camera Development Guide
How camera capture, viewfinder layout, and outer-display mirroring work when developing for iPhone Duo.
Last updated
Quick answer
Size the camera preview layer to the current view bounds — not a fixed aspect ratio — so it resizes as the device folds and unfolds. You can mirror the viewfinder to the outer display for subjects to see themselves, and should read the current interface orientation from the scene rather than locking capture orientation at launch.
Adaptive viewfinder
Camera apps built with AVCaptureVideoPreviewLayer should size the preview layer to the current view bounds rather than a fixed aspect ratio tied to a specific device. On Duo, the available capture surface changes as the device folds and unfolds, and the preview should resize along with it.
Outer display preview
A camera app can mirror the viewfinder to the outer display so subjects can see themselves while the photographer uses the inner display — useful for selfies taken with the rear camera. This uses the same multi-scene approach described in the Multiple Displays guide.
Orientation handling
Common mistake
Don't lock capture orientation to the device's physical orientation at launch. Read the current interface orientation from the scene and update capture connection orientation when it changes, since Duo poses make orientation changes more frequent than on a typical iPhone.
Frequently asked questions
Can I mirror the camera viewfinder to the outer display?
Yes. A camera app can mirror the viewfinder to iPhone Duo's outer display so subjects can see themselves while the photographer uses the inner display, using the same multi-scene approach as any other outer-display feature.
Should I lock capture orientation to the device orientation at launch?
No — don't lock it at launch. Read the current interface orientation from the scene and update the capture connection's orientation whenever it changes, since Duo poses make orientation changes more frequent than on a typical iPhone.
How should the camera viewfinder resize on iPhone Duo?
Size AVCaptureVideoPreviewLayer to the current view bounds rather than a fixed aspect ratio tied to a specific device, so the preview resizes correctly as the device folds and unfolds.