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Old 30th September 2018, 06:12   #11  |  Link
FranceBB
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Join Date: Nov 2013
Location: Germany
Posts: 688
New test and new comparisons!

Original HDR Source: Link
Normal HDR to SDR: Link
Scale default: Link

Hable: Link

Code:
ConvertBits(16)

ConvertYUVtoXYZ(Color=0, OutputMode=1, HDRMode=0, fullrange=false)

ConvertXYZ_Hable_HDRtoSDR(exposure_X=7.0)

ConvertXYZtoYUV(pColor=0)
Not bad at all, very close to the original.
Too bad for the object that Loki is holding: I got it too bright and details are lost.
I tried to play a bit with the white point, but I didn't manage to get it correct:

Hable v2: Link

Code:
ConvertBits(16)

ConvertYUVtoXYZ(Color=0, OutputMode=1, HDRMode=0, fullrange=false)

ConvertXYZ_Hable_HDRtoSDR(exposure_X=7.0, whitescale_X=8.0)

ConvertXYZtoYUV(pColor=0)
Mobius: https://i.imgur.com/tg8V3iF.jpg

Code:
ConvertBits(16)

ConvertYUVtoXYZ(Color=0, OutputMode=1, HDRMode=0, fullrange=false)

ConvertXYZ_Mobius_HDRtoSDR(exposure_X=17.0, peak_X=1.1)

ConvertXYZtoYUV(pColor=0)
Close, but I've got the same problem: the object is too bright and therefore I lose details...

And... here comes the star... here comes the good one... here comes the one that keeps details... here comes my favorite one:
Reinhard: Link

Code:
ConvertBits(16)

ConvertYUVtoXYZ(Color=0, OutputMode=1, HDRMode=0, fullrange=false)

ConvertXYZ_Reinhard_HDRtoSDR(exposure_X=2.5, contrast_X=0.9)

ConvertXYZtoYUV(pColor=0)
Just perfect, as I expected from Reinhard.
The exposure is exactly the same that I have on the HDR content and details of the object are not lost as I'm able to adjust the contrast accordingly. In my former chart I gave Reinhard an "A" and I'm gonna confirm my grade again.

Updated chart:

- ConvertXYZ_Scale_HDRtoSDR:

Grade: F

I gave it an F before because it didn't give me the correct values at all and I still gotta say that it's not fit for the job. Yes, it can be useful to test values and see how much you can scale down, but the result will be unwatchable anyway.

- ConvertXYZ_Hable_HDRtoSDR

Grade: C+

It's better than the "Scale" function, but I still think that it tries to "exasperate" the colors and give a sort of explosive fake HDR effect to the viewer at the expense of details which, for me, it's an absolute "no go".

- ConvertXYZ_Mobius_HDRtoSDR

Grade: B

It still tries to accentuate the "fake HDR feeling" by bringing colours a bit too saturated, but some people may like it. Overall, it's watchable for many people, but unfortunately, it loses some highlights. The kind of people that like these kind of grading probably doesn't care and actually prefers something like this, but it's simply not me.

- ConvertXYZ_Reinhard_HDRtoSDR

Grade: A

Reinhard gets the job done and it does it well, period.
It was my favorite one and it still is as today confirmed my thoughts once again.
Thanks to the contrast parameter and the exposure parameter it's possible to tweak it to get a very good result.
Yes, it's not gonna have extremely saturated colors and they will be perfectly legit for the BT709 range, the black level is gonna be pretty much perfect, details are gonna be kept and highlights are gonna be preserved.
Overall, it's my recommended way to do HDR to SDR.
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Last edited by FranceBB; 30th September 2018 at 17:54.
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