Re-occurring Power Window Bug

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Michael McCaffrey

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Re-occurring Power Window Bug

PostTue Feb 27, 2018 10:27 pm

I have had this happen on 3 or 4 occasions now. I create a new serial node and add a power window to a blown out part of the image, and dial back the highlights. But instead of the image returning to a normal exposure, the blown out areas go gray -- a clear indication that for some reason it is not accessing the image data from the original clip. Anyhow, Im not sure what's going on, but I have only seen this in Resolve 14.3 when it happens, sometimes Im unable to get the power windows to work and cant grade the image the way I want.

Some other things I've noticed:
- After applying the power window, at first it will work correctly, then doing almost anything else, like clicking the keyframe button will cause the fixed exposure to go gray.
- After applying the power window, it will work correctly, and I will hit the loop and play button and Resolve will cache the clip for playback, and while caching the clip, the power window maintains the correct exposure. But as soon as its cached through one time, it will begin playback at the beginning of the clip and the power window will go gray again.
- I was able to get Resolve to fix itself once, only by restarting my computer. (Restarting Resolve alone did not fix it)

Here is an example of my starting point. Its a dark shot so I raised the highlights and mid-tones, now I created a power window to reduce the highlights on the TV display:
Screen Shot 2018-02-27 at 2.26.33 PM.png
Screen Shot 2018-02-27 at 2.26.33 PM.png (53.04 KiB) Viewed 490 times


Here is an example of the image when it goes gray when reducing the highlights:
Screen Shot 2018-02-27 at 2.13.52 PM.png
Screen Shot 2018-02-27 at 2.13.52 PM.png (66.54 KiB) Viewed 490 times


Here is an example of how the image could look, if dialing back the highlights on the power window worked correctly:
Screen Shot 2018-02-27 at 2.14.05 PM.png
Screen Shot 2018-02-27 at 2.14.05 PM.png (66.61 KiB) Viewed 490 times
Configuration:
Resolve Studio 15.3.1
Windows 10 Pro
16 Core AMD Ryzen Threadripper 1950X. 64GB RAM
Dual GTX 1080 Ti's
24TB RAID
Intensity Pro 4k
(1) 1080P Display, (1) 27” Display, (1) HPz24 1080P Display for Grading
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Dwaine Maggart

Blackmagic Design

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Re: Re-occurring Power Window Bug

PostTue Feb 27, 2018 10:46 pm

That gray looks like you may have accidentally enabled the Resolve Highlight mode.
Dwaine Maggart
Blackmagic Design DaVinci Support
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Michael McCaffrey

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Re: Re-occurring Power Window Bug

PostTue Feb 27, 2018 11:39 pm

Dwaine Maggart wrote:That gray looks like you may have accidentally enabled the Resolve Highlight mode.


Yes it looks like that, but its definitely not. Have not touched the eye-dropper or enabled the highlight mode. What it looks like, is what happens when you try to recover some highlights and there is no data to recover -- so things just go gray. However, the data is definitely there and can be recovered if I remove the power window. Also it happened again after my last post. So now I have to restart my computer again. Would love to find out whats going on here.
Configuration:
Resolve Studio 15.3.1
Windows 10 Pro
16 Core AMD Ryzen Threadripper 1950X. 64GB RAM
Dual GTX 1080 Ti's
24TB RAID
Intensity Pro 4k
(1) 1080P Display, (1) 27” Display, (1) HPz24 1080P Display for Grading
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Michael McCaffrey

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Re: Re-occurring Power Window Bug

PostWed Feb 28, 2018 12:01 am

It shouldnt matter whether the power window comes before or after the main grade right?
Configuration:
Resolve Studio 15.3.1
Windows 10 Pro
16 Core AMD Ryzen Threadripper 1950X. 64GB RAM
Dual GTX 1080 Ti's
24TB RAID
Intensity Pro 4k
(1) 1080P Display, (1) 27” Display, (1) HPz24 1080P Display for Grading
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Michael McCaffrey

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  • Joined: Tue Apr 14, 2015 1:30 am

Re: Re-occurring Power Window Bug

PostWed Feb 28, 2018 12:04 am

Quick Video explaining the issue:
Configuration:
Resolve Studio 15.3.1
Windows 10 Pro
16 Core AMD Ryzen Threadripper 1950X. 64GB RAM
Dual GTX 1080 Ti's
24TB RAID
Intensity Pro 4k
(1) 1080P Display, (1) 27” Display, (1) HPz24 1080P Display for Grading
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Dwaine Maggart

Blackmagic Design

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  • Joined: Wed Aug 22, 2012 2:53 pm

Re: Re-occurring Power Window Bug

PostWed Feb 28, 2018 12:28 am

You have a LUT and Curve applied to node 1. Adjusting Gain on that node will have a much different affect then adjusting gain in the same amount on node 2, whether its in a window or not.

As a quick solution to what I think you are trying to do, add the second node by right clicking in the node area and selecting Add Node - Corrector.

Feed the Input that's going to node 1 input, to node 2 input as well.

Delete the output link on node 1.

So now you have the input going to the input side of node 1 and 2.

Right click in the node area, select Add Node - Layer Mixer. Send the output of node 1 to the top input of the Layer Mixer and the output of node 2 to the bottom of the Layer Mixer. Send the Layer Mixer output to the Output.

Make your window on node 2 and adjust it. I think you'll get what you want.

There are probably a dozen other ways to do this, and any actual colorists, feel free to chime in.
Dwaine Maggart
Blackmagic Design DaVinci Support
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Johan Fleetwood

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Re: Re-occurring Power Window Bug

PostWed Feb 28, 2018 9:40 am

Michael McCaffrey wrote:- After applying the power window, at first it will work correctly, then doing almost anything else, like clicking the keyframe button will cause the fixed exposure to go gray.
- After applying the power window, it will work correctly, and I will hit the loop and play button and Resolve will cache the clip for playback, and while caching the clip, the power window maintains the correct exposure. But as soon as its cached through one time, it will begin playback at the beginning of the clip and the power window will go gray again.


Check your cache settings, make sure to use a format/codec that doesn't clip the highlights.

Also, try adding a first node and reduce the highlights before doing anything else.
Johan Fleetwood
Colorist | Editor | Post Production Consultant
< Win10pro, RTX 2080, Decklink, Mini Panel, Ample RAM & SSD storage >
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roger.magnusson

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Re: Re-occurring Power Window Bug

PostWed Feb 28, 2018 11:32 am

Since he is using a LUT that clips the image, later nodes will clip regardless of caching format.
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Michael McCaffrey

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Re: Re-occurring Power Window Bug

PostWed Feb 28, 2018 4:08 pm

roger.magnusson wrote:Since he is using a LUT that clips the image, later nodes will clip regardless of caching format.



Yes I noticed that and removed the LUT and still had the same problem. Even on different shots where there was no LUT. I agree and can see how and why a LUT could potentially cause the problem and I was hoping that as it, but apparently even without the LUT the issue persists.
Configuration:
Resolve Studio 15.3.1
Windows 10 Pro
16 Core AMD Ryzen Threadripper 1950X. 64GB RAM
Dual GTX 1080 Ti's
24TB RAID
Intensity Pro 4k
(1) 1080P Display, (1) 27” Display, (1) HPz24 1080P Display for Grading
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roger.magnusson

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  • Location: Sweden

Re: Re-occurring Power Window Bug

PostWed Feb 28, 2018 7:51 pm

Then it might be the caching format/codec like Johan said!
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Michael McCaffrey

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Re: Re-occurring Power Window Bug

PostWed Feb 28, 2018 10:26 pm

Im using ProRes 422 as the cache codec. So I'd think that would be okay. Even the source material (shot on UM46k) is ProRes 422 and I am able to dial back the highlights just fine. Bear in mind the footage is only blown out because I boosted the mid-tones and highlights in grading, and then needed to subsequently dial back the highlights in the areas that got blown out by that adjustment.
Configuration:
Resolve Studio 15.3.1
Windows 10 Pro
16 Core AMD Ryzen Threadripper 1950X. 64GB RAM
Dual GTX 1080 Ti's
24TB RAID
Intensity Pro 4k
(1) 1080P Display, (1) 27” Display, (1) HPz24 1080P Display for Grading
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roger.magnusson

  • Posts: 915
  • Joined: Wed Sep 23, 2015 4:58 pm
  • Location: Sweden

Re: Re-occurring Power Window Bug

PostWed Feb 28, 2018 10:37 pm

Ah, you need to use at least ProRes 444 for the cache files I believe. More info here: http://vanhurkman.com/wordpress/?p=3471. Since the article was written BMD has added more codecs suitable for caching without clipping, but I don't think ProRes 422 is one of them.

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