Like many of you, I also noticed that turning on or off the HDR option on video section of the atv4k, changes the brightness on your tv. Not by a little, but by a lot. I didn't noticed at first because the lights were on, but when the room was dark, it was a different story. We all experienced the same thing with iTunes AAC... and the many people that, to this day claim there is not difference between AAC and Lossless. I will say this, aac doesn't sound too bad on cheap headphones (and yes, Beats are "cheap" headphones) Using Grado Rs1e, or Fostex TH900ii, you will hear a huge difference between aac and regular cds. I think the same thing is happening with iTunes 4k; because when I use the Atv4k on my very entry level Vizio 4k non hdr, it looks ok. But when I use the Atv4k on my Samsung 65 8000 better tv (better because when side by side playing SD HD or 4K wins hands down and not only by a little, even the wife noticed it, by a lot) iTunes 4k doesn't look good at all. So I guess I'm comparing this video signal to an audio signal since is what I know. You can feed crap music to cheap headphones and they sound ok. But you can NOT feed crap music to good headphones because they sound like crap, even worst than the cheaper headphones. (By cheaper I don't mean $$, I mean poorly design, cheaply made) I guess what I'm trying to say is: Feeding my Vizio with crappy 4k will look ok, But feeding crappy 4k to a tv that demands more will look crappy. Apples new formats are all about saving space. HECV and HEIC claim to have the same quality to 4k and jpeg... But they also said that about aac when they talk on the keynotes... I love Steve Jobs, but when he said that the Apple Hi Fi Boombox was for audiophiles, I started laughing so hard... But I understand... they are salesmen that need to make money.