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Author Topic: New ACR HDR - not the old older HDR  (Read 2377 times)

RMW

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New ACR HDR - not the old older HDR
« on: December 09, 2022, 01:05:06 pm »

Apologies if this is a repeat .

What is your experience with the new ACR HDR that substantially boosts recovery of highlights? This is not the older merging to HDR in PS. It requires making changes in Settings. And it might only be available on Macs right now.

I haven't tried it yet as I'm wary of fouling up my usual workflow.

Thanks All.

Richard
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mcbroomf

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Re: New ACR HDR - not the old older HDR
« Reply #1 on: December 09, 2022, 02:40:53 pm »

It's only available for screen/viewing (HDR screens with very high NITS) so no use for printing which makes it a miss for me.  The only application I see would be for high DR images to put on a web page but that would mean everyone would need an HDR screen and I'd hazard a guess that will never happen.  I use HDR tonemaping (what you called Old HDR) quite a bit and I'm pretty happy with it now that the garish look is gone.
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digitaldog

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Re: New ACR HDR - not the old older HDR
« Reply #2 on: December 09, 2022, 03:14:09 pm »

Actual highlights that are clipped in the raw; can't be recovered. They are gone.
Highlights that appear clipped that are not in the raw, that's different.
ACR engine can take one channel that isn't clipped in the raw and recreate the other two, but it's not magic and not ideal compared to simply not clipping channel data.
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Tuco

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Re: New ACR HDR - not the old older HDR
« Reply #3 on: December 09, 2022, 03:48:38 pm »

What is your experience with the new ACR HDR that substantially boosts recovery of highlights?

It's fun to revisit your old raw library in HDR mode, but with no workflow that I'm aware of to save and display them properly on a capable phone/tablet it's fun waste of time (competing standards and Apple's flaky implementation of avif, etc. are to blame).  Not relevant for print workflows unless you want to be disappointed at what you're missing as you squash that dynamic range onto a standard image file or print.
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digitaldog

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Re: New ACR HDR - not the old older HDR
« Reply #4 on: December 09, 2022, 03:57:59 pm »

The new HDR functionality in ACR is only for the display. Internally ACR always handles HDR data (e.g., being able to read DNG files created from Merge to HDR, or other external HDR content created in other apps); it's only the output that is always mapped to SDR but now, there is an option due to HDR displays (far and few).
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RMW

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Re: New ACR HDR - not the old older HDR
« Reply #5 on: December 10, 2022, 11:41:12 am »

Thank you all for making this known.
Richard
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fdisilvestro

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Re: New ACR HDR - not the old older HDR
« Reply #6 on: December 13, 2022, 01:23:40 pm »

Now available on windows (if you have a HDR-capable monitor) and the option to save in jpeg-XL or AVIF

MauriceRR

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Re: New ACR HDR - not the old older HDR
« Reply #7 on: February 05, 2023, 03:30:11 am »

Hello,
is someone having more info on that ? (internally -> HLG ? PQ ? ) In comparison with sdr, they only use highlights (cancelling the roll-off) instead of increasing in the same time the target exposure. Same behavior as video pipelines (on Davinci). Why not increasing also global target exposure in the same time ? (as a brighter screen would do in sdr...).
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Dave Ellis

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Re: New ACR HDR - not the old older HDR
« Reply #8 on: February 05, 2023, 05:44:27 pm »

Hello,
is someone having more info on that ? (internally -> HLG ? PQ ? ) In comparison with sdr, they only use highlights (cancelling the roll-off) instead of increasing in the same time the target exposure. Same behavior as video pipelines (on Davinci). Why not increasing also global target exposure in the same time ? (as a brighter screen would do in sdr...).

I don't think transfer functions like HLG and PQ are used with the internal processing of HDRO in ACR. My understanding is that it's all done in 32 bit floating point. On the other hand, when you export an HDRO file say in avif format, either HLG or PQ is used. I think ACR uses PQ.

There is a standard under development, see here.

I'm not sure what you mean with your comments on exposure. The best you can do is expose to the right without any highlight clipping. As I see it, ACR expands the highlights above SDR standard white when the HDR button is pressed. This undoes the compression in this area caused by the tone curve used. The tone curve still improves the contrast in the SDR part of the image.

Dave
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MauriceRR

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Re: New ACR HDR - not the old older HDR
« Reply #9 on: February 18, 2023, 01:44:03 pm »

I don't think transfer functions like HLG and PQ are used with the internal processing of HDRO in ACR. My understanding is that it's all done in 32 bit floating point. On the other hand, when you export an HDRO file say in avif format, either HLG or PQ is used. I think ACR uses PQ.

There is a standard under development, see here.

I'm not sure what you mean with your comments on exposure. The best you can do is expose to the right without any highlight clipping. As I see it, ACR expands the highlights above SDR standard white when the HDR button is pressed. This undoes the compression in this area caused by the tone curve used. The tone curve still improves the contrast in the SDR part of the image.

Dave
Yes, true on many points. Sorry for my late reply.
Yes, I imagine it's done internally with floating 32.
By "target exposure", I meaned same brightness for mid-grey.
However, and if I compare with Davinci resolve for example, my guess is that there is a conversion for displaing the datas, and this conversion need to be function of the choosen display curve of the display (HLG or PQ).
The way it is done with SDR worflow (AFIK) is that the curve (linear light -> rec709alikee) is mainly handle in the dcp profile, so I'm pretty confused by this one click "hdr" button in the user interface.


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Dave Ellis

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Re: New ACR HDR - not the old older HDR
« Reply #10 on: February 18, 2023, 05:13:18 pm »

Yes, true on many points. Sorry for my late reply.
Yes, I imagine it's done internally with floating 32.
By "target exposure", I meaned same brightness for mid-grey.
However, and if I compare with Davinci resolve for example, my guess is that there is a conversion for displaing the datas, and this conversion need to be function of the choosen display curve of the display (HLG or PQ).
The way it is done with SDR worflow (AFIK) is that the curve (linear light -> rec709alikee) is mainly handle in the dcp profile, so I'm pretty confused by this one click "hdr" button in the user interface.

With Windows, it seems to use HDR10 as the display interface (which in turn uses the PQ transfer function). On my Macbook Pro I'm not sure. I've assumed that as the interface is all internal it uses 32 bit float and converts to linear 10 bit for the display but I could be wrong. Not sure about the Mac interface to an external Mac XDR display, but a quick test with my Macbook and an HDR TV indicates it might also be HDR10.

Edit: Just found an Apple White paper on their 22" XDR display which confirms that the transfer function used for the HDR interface is PQ (not specifically HDR10 but the same transfer function).

Dave
« Last Edit: February 19, 2023, 07:50:27 pm by Dave Ellis »
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