the camera can be started within a second by pressing the power button on the Samsung device twice in quick succession. the quick start works both in idle mode (display off) and during use. it is also activated by default on Samsung devices, but can also be deactivated in the camera settings.
Devices with function key
On Samsung devices that have a function key (basically the power key), the key assignment may need to be changed (see Android 10/One Ui 2 manual)
- Open the Settings
- Tap on Advanced features
- Tap on Side key
- Enable Double press and choose Quick launch camera