2016-05-01, 00:42
(2016-04-30, 03:54)Soli Wrote: In laymans terms (or the best I can do without going all techie) Displays in HDR mode use a different gamma curve, so the relative bitlevels are much slower going from dark to bright. That's why a HDR picture will look too bright on a normal display. When using a display in HDR mode with the darker gamma curve, it will look right.
So, to convert a HDR picture to SDR, you need to do the opposite:adjust the picture to be darker so it will look right on a normal SDR display. But you leave out the HDR part of the image, or it wont "fit". I am not sure but I suspect different manufacturers have slightly different methods to convert HDR to SDR as I think there is no definitive standard to this, and different manufacturers might want to be clever and keep parts of HDR when downconverting. (Again, I haven't read up on the specifics although it's pretty straightforward mathemathically) Let's call this the secret sauce. The sauce is used when downconverting to SDR. Another sauce is in place when the display switch over to HDR mode.
HDR is still a mess , and the HDR metadata are dynamic; describing both max luminence and also the color gamut. So the display has to somehow switch gamma/modes/gamut on the fly. A very special sauce indeed, and for the time being pretty much impossible to calibrate properly (although I have a rough idea on how they are going to solve this)
(2016-04-30, 14:39)gbakay Wrote:(2016-04-30, 01:52)OlivierQC Wrote: Hello gbakay
sony x93c is compatible HDR since september 2015, i will take picture when my tv switch in HDR mode or i will make a video.
My wrong Oliver, you lucky guy, wish my X900B had HDR When you do get a chance I would love to see pictures or video in HDR mode.
AIUI different HDR solutions have different routes to SDR compatibility.
It's a key issue for broadcasters - who don't want to be in the situations of simulcasting HDR and SDR duplicate content and need an SDR-compatible HDR system (like B&W SD TVs were - apart from some in the UK and France - compatible with colour transmissions)
The BBC & NHK have proposed a Hybrid Log Gamma system that displays a compatible image acceptably on an SDR display, but on a suitable HDR display you get the benefit of the greater dynamic range. It also allows for live multi camera production (again vital for broadcast), which has still yet to be seen demonstrated (or hadn't pre-NAB) for Dolby Vision. (Their 'live' claims were apparently all single camera...) I've seen it demo-ed and it certainly delivered SDR and HDR pictures from a single signal.