Dim Apple TV HDR on an LG C3 (and C2/C1) is a known, fixable combo — not a bad panel or box. (For the general, brand-agnostic version of this, see Apple TV HDR looks dark or wrong.) Two things stack up: the Apple TV forces Dolby Vision onto everything, and the C3's Dolby Vision picture mode can render dark, especially in a bright room. Add HDMI Deep Color being off and the picture looks dim and flat. Here's the LG-specific fix.
Fix it
- Turn on HDMI Deep Color for that port — do this first. Settings > General > Devices > HDMI Settings > HDMI Deep Color = On for the input the Apple TV is on. Without it the port runs a reduced mode and HDR looks dim/banded.
- Pick the brighter Dolby Vision mode on the C3. With Dolby Vision content playing, set the C3 picture mode to Dolby Vision Cinema Home (or Dolby Vision IMAX/Vivid) rather than Dolby Vision Cinema, which is accurate but dark. Then raise OLED Pixel Brightness / Peak Brightness (High).
- Stop the Apple TV forcing Dolby Vision on everything. Apple TV > Settings > Video and Audio > Format > 4K SDR, and Match Content > Match Dynamic Range = On. Now the C3 only enters Dolby Vision for genuine DV content instead of applying DV tone-mapping (the dark look) to SDR/HDR10.
- Turn off the C3's auto dimmer. Settings > Support > Energy Saving = Off (and any Auto Brightness / ambient sensor), which otherwise dims the panel and fights HDR brightness.
Why this specific combo looks dark
The LG C3's Dolby Vision Cinema preset targets a dark room and runs dim; when the Apple TV forces everything into Dolby Vision, even SDR and HDR10 content gets that dark DV treatment. Switching the Apple TV base to 4K SDR + Match Dynamic Range hands the C3 the correct format per title, and choosing a brighter DV mode fixes the genuinely-DV content.
If it's still dim
- Raise OLED Pixel Brightness and Peak Brightness within the HDR/DV preset — OLED presets ship conservative.
- Use a certified Ultra High Speed cable — a marginal one drops HDR metadata, which the C3 shows as flat/dim.
- Try HDR10 instead of DV for a test: set the Apple TV format to 4K SDR (HDR10 auto) — if HDR10 looks better than DV on your C3, that confirms the DV mode was the dim culprit.
FAQ
Why is Apple TV HDR so dark on my LG C3? The C3's Dolby Vision Cinema mode is dark, and the Apple TV forces DV on everything. Switch to Dolby Vision Cinema Home (brighter), set the Apple TV to 4K SDR + Match Dynamic Range, and turn on HDMI Deep Color.
Which Dolby Vision mode should I use on the C3? Dolby Vision Cinema Home (or IMAX/Vivid) for a bright room — Cinema is accurate but dim. Raise peak brightness within it.
Should the Apple TV be on Dolby Vision or SDR? Set it to 4K SDR with Match Dynamic Range on, so the C3 enters DV only for real DV content instead of darkening everything.
It's still dim after that. Raise OLED Pixel/Peak Brightness, turn off Energy Saving, and confirm HDMI Deep Color is on with a certified cable.