Blotchy gradients and posterization happen when HDR tone mapping or bandwidth is off. Use these steps to clean up color and restore smooth gradients.
Quick answer
- Use the TV’s 4K/HDMI 2.1 port with a certified cable; reseat both ends.
- Set Apple TV to 4K SDR 60 Hz with Match Dynamic Range/Frame Rate On; enable HDR/Dolby Vision only after stability.
- Choose a Cinema/Filmmaker picture mode, disable vivid/demo modes, and enable the input’s Enhanced/Deep Color setting.
- Turn off heavy dynamic contrast/noise reduction while tuning.
Symptoms
- Sky gradients look striped or blocky in HDR/Dolby Vision.
- Colors shift or posterize when switching apps or frame rates.
- HDR looks dim or overly saturated compared to SDR.
Quick checks
- Confirm the TV input is in Enhanced/Deep Color/HDMI 2.1 mode.
- Swap to a certified HDMI 2.1 cable to rule out bandwidth loss.
- On Apple TV, run Check HDMI Connection to verify HDR capability.
- Avoid vivid/dynamic picture modes while testing.
Step-by-step fix
- Stabilize the HDMI path – Apple TV on the TV’s 4K/eARC port with a certified cable. Recommended: Certified Ultra High Speed HDMI cable (paid link).
- Set a clean base mode – Apple TV: 4K SDR 60 Hz, Match Dynamic Range/Frame Rate On, Chroma 4:2:0. Verify SDR is clean.
- Enable HDR and tune picture mode – Turn on HDR/Dolby Vision. Choose Cinema/Filmmaker/Movie; set color temperature to Warm, disable Dynamic Contrast/Noise Reduction while testing.
- Check black/white levels – Set HDMI Black Level to Auto/Normal. Reduce contrast if highlights clip; raise shadow detail slightly if blacks crush.
- Separate presets per format – Many TVs store separate settings for Dolby Vision vs HDR10; tune each mode after enabling it.
If banding persists
- Try 4:2:0 chroma and 10-bit output; avoid forcing RGB High unless the TV requires it.
- Turn off motion smoothing and MPEG noise reduction, which can exaggerate gradients.
- Test another HDR source (disc/console). If only Apple TV shows banding, reinstall apps and retest.
- If Dolby Vision remains dim, use HDR10 for that app until a firmware update arrives.
FAQ
Why does SDR look fine but HDR bands? HDR uses higher bit depth and tone mapping; if the port is not in Enhanced mode or the cable is marginal, data is reduced and gradients break.
Should I force 4:2:2 or RGB? Start with 4:2:0 for stability; only move to 4:2:2/RGB if the TV and cable reliably pass it.
Can Match Content help? Yes. It prevents the UI from forcing HDR on SDR apps, which often causes odd colors and banding.
Do I need calibration? Usually no. A good preset with correct port mode and cable fixes most banding. Calibrate only if you want fine accuracy.