I started talking about this in an old thread in here cos I noticed someone else had come to the same conclusion I have. Apple TV hdmi output is labelled opposite to most other devices.
I have seen a lot of misinformation about this online and just wanted to put it out there for anyone else looking to set it right that Apple TV has the settings backwards to what most other devices use.
Apple TV is
Rgb high = 16-235 (tv standard) and TVs should be set to limited
Rgb low = 0-255 (pc standard) and Tv should be set to full.
There's also a pretty simple rule to follow.
You can't have crushed blacks when the tv is set to full range, it will either be washed out or correct. So set tv to full range and try Apple TV set to low and it will be correct, then switch Apple TV to high and the whites and blacks will be washed out.
The same applies for setting the tv to limited except this time you can't have washed out blacks/whites, but instead you will only see crushed blacks when set incorrectly. So set tv to limited and set Apple TV to low and you will see crushed blacks. Switch Apple TV to high and it will be correct.
Easy to verify for yourselves.
Easiest test pattern to use while checking those settings is probably this one..
I can verify that video shows the differences correctly.
After doing that test for yourselves you will see that setting the tv to full range and Apple TV to low will have the same correct image as setting the TV to limited and Apple TV to high.
And you will also see that setting the tv to full and Apple TV to high will give you washed out blacks just as setting the tv to limited and Apple TV to low will give you crushed blacks thus confirming that on Apple TV rgb high = 16-235 and rgb low = 0-255.
I also posted this thread on reddit, as I find the confusion around hdmi range very annoying and don't like seeing misinformation passed around. And a lot of people would be setting the hdmi range for Apple TV incorrectly based on what all their other devices list these settings as making the calibration worthless.