How to adjust the focal length with OPPO mobile phone?

Method for adjusting focal length of OPPO mobile phone:

You can focus by pressing the screen. Click it to enlarge it, and click it again to restore it.

Press the button for a long time, and the zoom adjustment bar will expand. You can slide the zoom screen with two fingers and adjust the focal length freely.

Enter Settings-Camera, and the function controlled by the volume key can be set to zoom. When taking pictures, press the volume key to increase the focal length, and press the volume key to decrease the focal length.

Note: The operation path refers to ColorOS 6 system.