[benabbottnz]

https://webkit.org/blog-files/color-gamut/

Look at the second example ( red images) and click the Display P3 option.

Do you see the symbol inside? No? Well then your display / monitor isn’t capable of showing a colour range higher than sRGB.

HDR is similar in respect to brightness and contrast.

If your device supports HDR, then there’s more steps in the brightness scale that your monitor can display.

[stavros]

Is higher granularity all HDR is, then? Other commenters mention that the HDR brightness max is more than what the SDR brightness max is defined as, which seems odd to me. It's as if you're crippling the display for SDR permanently.

[skavi]

Rec.709 actually defines a peak luma of 100 nits. sRGB has it defined as 80 nits. These numbers are really only for mastering, but as you push further from the standard you start to see artifacts, namely banding in gradients.

HDR standards require higher bit depth and define higher peak brightness. In addition, and this is probably technically the toughest bit, they define dynamic metadata formats which define tone mapping as the content changes [0].

One thing you may be missing about the particular effect we see on this website is that it disappears as you turn your device brightness up. So you can still get that brightness with SDR content.

[0]: https://www.avforums.com/articles/what-is-4k-hdr-dynamic-met...

[Dylan16807]

Ideal HDR goes up to 10000 nits or higher. It would be ridiculous to put SDR white anywhere near that level.

And there is no need to cripple anything. Brightness adjustment can/should let you put SDR white all the way up to the max full-screen brightness. If a manufacturer cripples that it's not HDR's fault.

But it's also important to note that "max full-screen brightness" is often a lot less than maximum spot brightness.