Huawei Mate 8 - Manual (Page 118)

Camera and Gallery
111
3
Focus on the subject (for example, PPT, poster, or screen), and then touch to take
a photo. Your phone will automatically extract the part of the image containing text
and adjust its orientation so that it is easier to read.
Ultra Snapshot
Press the volume down button twice to take a photo, even when the screen is off.
This feature is not available during music playback.
1
Open Camera.
2
Touch > > Ultra snapshot, and then select Open camera and take quick
snapshot. Select Off to disable this feature.
3
Point the camera at the desired object, and then press the volume down button twice
in quick succession. The camera will automatically take a photo and display the
capture time.