HDR - how well does your TV display the correct artistic intent? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 5 Old 01-13-2020, 07:19 AM - Thread Starter
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HDR - how well does your TV display the correct artistic intent?

A simple fact is all HDR grading is done on static displays, without any metadata or tone mapping - dynamic, or not.
(HDR grading displays simply clip at their peak luma - no roll-off, no tone mapping, no nothing!)

So, if your home TV matches, or betters, the peak luma of the grading/mastering display there is no need for any metadata, and no tone mapping/roll-off should be applied.

And as a lot of HDR material is graded at 1000 nits peak, there are a number of HDR TVs that can match/better this.

In simple terms, HDR10 should provide the best possible match to the original artistic intent, as there is no need for any metadata based manipulation on playback at all.

So...

If the implementations of Dolby Vision and HDR10+ are correct, they should also match the HDR10 playback, and in turn match (as well as possible based on the limitations of the specific TV) the original artistic intent.

Anyone fancy placing bets on the likelihood of this being the actual reality of how your TV implements HDR?

For additional info see: https://www.lightillusion.com/uhdtv.html

Steve

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post #2 of 5 Old 01-13-2020, 11:33 AM
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Quote:
Originally Posted by Light Illusion View Post
A simple fact is all HDR grading is done on static displays, without any metadata or tone mapping - dynamic, or not.
(HDR grading displays simply clip at their peak luma - no roll-off, no tone mapping, no nothing!)

So, if your home TV matches, or betters, the peak luma of the grading/mastering display there is no need for any metadata, and no tone mapping/roll-off should be applied.

And as a lot of HDR material is graded at 1000 nits peak, there are a number of HDR TVs that can match/better this.

In simple terms, HDR10 should provide the best possible match to the original artistic intent, as there is no need for any metadata based manipulation on playback at all.

So...

If the implementations of Dolby Vision and HDR10+ are correct, they should also match the HDR10 playback, and in turn match (as well as possible based on the limitations of the specific TV) the original artistic intent.

Anyone fancy placing bets on the likelihood of this being the actual reality of how your TV implements HDR?

For additional info see: https://www.lightillusion.com/uhdtv.html

Steve

Interesting read but the log-scaled PQ EOTF graph is not quite correct.




It cannot be a straight line (unless the PQ EOTF is pure logarithmic, which is not the case). The correct graph looks like this (and there is a correct graph on the same page, under Peak Luminance & Bit Levels).



Also, to say "This is one of the main issues with PQ based HDR - the overall picture brightness is a lot lower than most home users are used to, making viewing in normal bright 'living room' conditions very difficult" and attribute this to the the difference in shape between PQ EOTF and Gamma 2.4 is really misleading, and contradicts the statement made earlier in the article,

Quote:
Note that the APL (Average Picture Level) remains approximately consistent between the SDR and ST2084 HDR images, with just the contrast range and specular highlight levels increasing.
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post #3 of 5 Old 01-13-2020, 11:54 AM - Thread Starter
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The 'Log' graph is not a version of PQ - it is light, which is logarithmic.

And yes, the PQ image is/was a lot darker, due to the EOTF.
That is one of the reasons the diffuse white point was changed to ~200 nits, from the original 100 nits.
The issue is Absolute vs. Relative standards.
No average home SDR TV is 100 nits peak.

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post #4 of 5 Old 01-13-2020, 12:40 PM
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Quote:
Originally Posted by Light Illusion View Post
The 'Log' graph is not a version of PQ - it is light, which is logarithmic.

I just knew you were going to say that.


But, look at what is presented to the reader:





Quote:

If we change the graph to show Log scaling, so the output is perceptually correct for the human eye, we get the following.



I don't see how anyone would know the second graph is meant to show "light" and not the logarithmic version of the first graph.


Quote:
And yes, the PQ image is/was a lot darker, due to the EOTF.
Then can you please explain what this graph shows, which accompanies the note
Quote: Note that the APL (Average Picture Level) remains approximately consistent between the SDR and ST2084 HDR images



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post #5 of 5 Old 01-13-2020, 12:52 PM - Thread Starter
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Yeah, I could word that better.
But actually it's not really that relevant.
The key is the relative change in perceived brightness as seen by the HVS.

And the SDR/HDR graphs is basically self explanatory.
But, was drawn when 100 nits was the target diffuse white.
I've never got around to re-doing it.
(And is obviously based on light too.)

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