Many smart TVs use an ambient light sensor to change screen brightness automatically as the room gets lighter or darker. It can save a little power, but it can also make the picture dim at night or jump brighter when a lamp turns on.
These steps apply to Samsung, LG, Sony, and Vizio smart TVs that include a light sensor, especially models from roughly 2018 onward.
Does this affect you?
Use this if the TV picture changes brightness by itself even when the scene on screen has not changed. If brightness shifts only when HDR starts, that is the TV switching into HDR mode, not auto brightness.
Samsung: turn off Eco Sensor or Ambient Light Detection
- Open Settings.
- On older Tizen models, go to General > Eco Solution. On newer models, go to All Settings > General > Power and Energy Saving.
- Turn off Eco Sensor, Ambient Light Detection, or Brightness Optimization.
- Open Settings > Picture > Expert Settings and set Brightness manually.
If brightness still changes, also check Settings > General > Intelligent Mode for Adaptive Picture or similar automatic picture tuning and turn it off.
LG: turn off Energy Saving or Light Sensor
- Open Settings > All Settings > General.
- Go to Eco or Energy Saving.
- Set Energy Saving Step to Off, not Auto, Minimum, Medium, or Maximum.
- If your model has Settings > Picture > Additional Settings > Light Sensor, turn that off too.
- Set Picture Mode and Brightness or OLED Light manually afterward.
On many LG webOS TVs, the light sensor is tied to Energy Saving rather than a separate brightness toggle.
Sony and Vizio: disable the light sensor
- Sony Bravia/Google TV: Settings > Display & Sound > Picture > Advanced Settings > Light Sensor > Off.
- Vizio SmartCast: Settings > Picture > More, then turn off Ambient Light Sensor or Auto Brightness Control if available.
After disabling the sensor, set Backlight, Brightness, or OLED Light to the level you prefer.
If brightness still changes
Check Dynamic Contrast, Contrast Enhancer, Local Dimming, Adaptive Picture, or similar picture processing. These change brightness based on the scene itself instead of the room light, but they can look like the same issue.
Disabling automatic brightness may use slightly more power if you keep the backlight high, but for most households the difference is small.
Sources
- Samsung Support – Turn off Eco Sensor / Ambient Light Detection (2025)
- LG Support – Energy Saving and Ambient Light Sensor settings (2025)
- Sony Support – Disable Light Sensor on Bravia TVs (2025)