Camera

Tap Edit, then tap the Depth Control button at the top of the screen to adjust Depth Control or Portrait Lighting button to adjust Portrait Lighting. A slider appears below the photo. Drag the slider left or right to adjust the effect.

Use Portrait mode on your iPhone - Apple Support

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If you are experiencing issues with the depth effect not working on your iPhone 7 Plus, there could be several reasons for this:

1. Camera Settings: Make sure that the camera settings are set to "Portrait" mode. To do this, open the Camera app and swipe to the left until you see the "Portrait" option. If this option is not available, it could be due to an outdated software or a hardware issue.
2. Lighting Conditions: The depth effect on the iPhone 7 Plus relies on the lighting conditions of the scene. Make sure that you have adequate lighting for the subject, as low light conditions can affect the camera's ability to detect depth.
3. Distance: The iPhone 7 Plus needs to be a certain distance away from the subject to capture the depth effect. Make sure that you are not too close or too far away from the subject.
4. Obstructions: The depth effect on the iPhone 7 Plus may not work properly if there are obstructions in the scene, such as people or objects blocking the subject.