Samsung
Keep Screen On While Viewing: Turn On or Off auf Samsung
Keep screen on while viewing is part of the Motions and gestures options inside Advanced features on Samsung phones. It relies on the front camera to check whether you are looking at the display, and keeps it lit as long as it detects your face.
This is useful when you are reading a long article or following a recipe and do not want the screen to lock every few seconds. It becomes annoying when the camera misreads a face in low light or through glasses, keeping the display on longer than needed and using extra battery.
Where to find the setting
Open Tap on Settings ➔ Tap on Advanced features ➔ Tap on Motions and gestures ➔ Enable or disable Keep screen on while viewing. Toggle the switch to turn the feature on or off, depending on whether you want the camera to keep tracking your gaze.
If your screen keeps timing out too fast even with this feature enabled, check your regular screen timeout setting separately, since both work together to decide when the display locks.
Turn the feature off if you notice the front camera activating often for no reason, or if you prefer to save battery over convenience. Turn it back on if you frequently lose your place while reading because the screen locks too quickly.