If your LG TV’s screen is too dark or the brightness keeps changing, you’ll need to adjust the Energy Saving mode setting. By default, LG sets the Energy Saving to Auto, which means that the TV will automatically adjust the screen brightness depending on the ambient light it senses. This will save you energy usage. However, it can make your screen too dark to enjoy. And if your room lighting is constantly changing throughout the day, it will cause your TV to change its brightness while you’re watching.
To make your LG TV more enjoyable, go to Settings > Advance > Picture. Select the Energy Saving option and either set it to Low or Turn it off. If you turn it completely off, you should notice a brighter screen and the brightness will remain constant now. There you go. Enjoy your LG TV.