Based on what I can see the ATV 4k is doing a pretty good job at whatever conversion it is doing. I have three streaming devices connected in my home theater, ATV 4k, Nvidia Shield, and a FireTV Stick 4k all going thru a Denon x6400h to a Optoma UHZ65 4k laser projector. Using NetFlix on each I ran The Umbrella Academy episode 1 from approximately minute 19 to minute 24 which has lots of dark, light, contrast, and colors particularly in the bar/sitting area scene. I really could discern very little difference between any of them....for what it’s worth. Of course it’s hard doing a good comparison flipping back and forth and not doing a real side by side but it’s the best I could do. According to NetFlix the source on the ATV 4k was DV and on both the Shield and FireTV, HDR.