Why does Samsung TV screen turn dark while watching?
● Resolving Dark or Dim picture is usually just a matter of adjusting settings.
2. Change the Picture Mode (Highest Brightness mode)
3. Disable Ambient Light Detection function
Older Models: System > Eco Solution > Eco Sensor > select On or Off
Newer Models: Settings > General > Ambient Light Detection > use the slider to turn on or off.
The Ambient Light Detection function (also called ECO Sensor on some older models) measures the light in the room and changes the screen brightness automatically to reduce power consumption. The screen will be brighter in a brightly lit room and darker in a dark room.
4. It can be caused by weak signal strength and signal quality of connected device.
Check Signal Information: Home (Menu) > Settings > Support > Self Diagnosis > Signal Information
You need to check the connected device and connected cable and replace if the problem is caused due to cable.