If you're not enabling HDR in Windows, then there will be no difference to what you had before. You're still using the same tone-mapping, with the same results. The 'improvement' is the ability to use the D3D swapchain for HDR in Windows 10. If you don't enable HDR, the colorspace is detected and set to sRGB (SDR bt.709) not PQ (SMPTE 2084), and mpv will tone-map. When the swapchain is set to PQ, then you get this:
The automatic switching between SDR and HDR, is a Windows 10 mechanism, which at this time, is not being employed. Even if mpv were to employ it, Theater in its present state, won't allow full screen exclusivity and so it couldn't be used, anyway.
Edited by Doofus, 24 March 2020 - 01:47 AM.