This phenomenon occurs because the Dynamic Backlight Control function is adjusting the brightness of the screen when menu items (on-screen displays) or subtitles are detected.
If this phenomenon bothers you, perform the following procedure.
- Press the HOME button on the remote control.
- Select Settings.
- Select Display in the TV category.
- Select Picture.
- Select Advanced settings.
- Select Brightness.
- Set Adv. contrast enhancer to Low or Off.