Diagnosis
The TV's picture settings aren't optimized for HDR content, which requires different brightness and contrast than standard shows. The default settings often leave HDR looking dim.
How to Fix It
You need to adjust the picture mode specifically for HDR. First, start playing an HDR show (look for the HDR or Dolby Vision icon). While it's playing, press the Settings button and go to Picture. You'll see the mode is likely "HDR Vivid" or "HDR Cinema." Select "Expert (Dark Room)" for the most accurate image. Now, go into Picture Mode Settings. Make sure "Energy Saving" is OFF. Set OLED Pixel Brightness to 80-100. Set Contrast to 100. Leave Brightness at 50. Set Gamma to 2.2. For Color, set Depth to 55-60. Under Clarity, turn OFF Super Resolution and set Noise Reduction to Low.
If That Didn't Work
The issue might be in the app itself. For the built-in apps, try clearing the cache. Go to All Settings > General > System > Storage & Reset. Select "Internal Storage," then find the app (like Netflix) and select "Clear Cache." Do not select "Clear Data" or you'll have to log back in.
Heads Up
HDR is designed for darker rooms. In a bright room, it will always look somewhat dim compared to a super-bright, oversaturated SDR image. This is normal. Give your eyes a minute to adjust—you'll see more shadow detail.