HDR600 etc are not just a maximum required brightness but also a minimum required black value. That gives you an actual dynamic range; 10bit is not a range, it's a resolution.
HDR10 is a 10bit color depth. Not resolution. 1080p is generally considered minimum resolution, but that has nothing to do with the "10bit" part of HDR10: HDR10 Media Profile, more commonly known as HDR10, was announced on August 27, 2015, by the Consumer Technology Association and uses the wide-gamut Rec. 2020 color space, a bit depth of 10-bits [0]
Also, no, the 400/600 etc is just brightness: HDR10 and HDR 400 are the same, except HDR 400 mentions the level of brightness on the display. [1].
You may be thinking of HDR True Black, which is a further enhancement, but something different. Deeper blacks can also be achieved by non-OLED displays that support full-array local dimming, and it looks like most displays that support FALD are also HDR displays.
> Also, no, the 400/600 etc is just brightness: HDR10 and HDR 400 are the same, except HDR 400 mentions the level of brightness on the display. [1].
Vesa [0] disagrees with you. Note the Maximum
Black Level Luminance restrictions. Minimum brightness + maximum black level = minimum contrast. That's why legacy display technologies with mediocre static contrast (TN, VA, IPS) need backlight hacks to support those specifications.
Also, no, the 400/600 etc is just brightness: HDR10 and HDR 400 are the same, except HDR 400 mentions the level of brightness on the display. [1].
You may be thinking of HDR True Black, which is a further enhancement, but something different. Deeper blacks can also be achieved by non-OLED displays that support full-array local dimming, and it looks like most displays that support FALD are also HDR displays.
[0]https://en.m.wikipedia.org/wiki/High-dynamic-range_video
[1]https://www.bluecinetech.co.uk/hdr10-vs-hdr400/#:~:text=HDR-...