EXR Artefacts

Hi all,

I am currently color grading a CGI shot I am working on using Davinci Resolve. I am very new to this software and color grading in general, so please excuse any obvious mistakes.

Davinci Resolve 17 (Free)Windows 10, Version 21H2CPU: i7-6700KGPU: GTX 1070RAM: 64GB

I am working with an EXR sequence, exported from the 3D software Blender. When importing the EXR sequence into Davinci Resolve, it displays very dark. To fix this, I use the VFX IO LUT "Linear to Gamma 2.2". This makes the image look like the render output from Blender. (I have tried using the Color space transform effect instead of a LUT but that doesnt solve the issue either)

Unfortunately, this causes weird artefacts in the highlights of the image (around the headlights).

These artefacts do not occur when importing the sequence into After Effects.

Can anyone explain to me what I am doing wrong and how to fix this, as it clearly doesn't seem to be a rendering issue from Blender 3D, but a color issue within Davinci.

I would appreciate any help I can get.

Thanks,

- CB

Here is another example of the artefact around the headlights

Can you upload a single frame so we can see if it's the LUT or Davinci that causes a problem?

unfortunately the extension EXR is not allowed by the forum to be uploaded. Here is a Google Drive link to the single frame EXR:
https://drive.google.com/file/d/1RVEkfJ ... sp=sharing

Thanks.

So the problem is the LUT.
If you use Davinci Color managed and set the Input Color Space to Linear, you get the full value of EXR.

gamma+0.11, Gain+2.27

Untitled.png (656.04 KiB) Viewed 1745 times

Glad to see there is a solution. Where do I find the option for "Davinci Color Managed"? Is that a node in the color settings, or where do I apply it?

(I recommend that you watch the rest of the training videos from Blackmagic, as well as read the manual)

Wow okay I think I got it. Thanks a bunch! I've included a screenshot of my color managed settings - I hope I did everything right here?

I have the same problem, settings as in the attached screenshot do not solve it for me.
The EXR is a particular one, it was converted from an *.hdr file which made with a 20 year old plugin.
However in Photoshop everything looks fine.

If I choose an input lookup table in project settings the problem is gone, but so is HDR...

Attached are some screenshot crops that explain the problem.

Resolve-EXR-highlight.png (462.33 KiB) Viewed 1609 times

The issue is likely because of scaling algorithms creating negative values in those areas because they might only work properly with ranges between 0-1 float.
You can verify this by turning the scaling off on that image and see if the problem persists. To mitigate the issue use a different scaling algorithm project wide or for those specific clips, or work in a timeline that matches the resolution of the EXRs.
Project wide scaling is found under Image Scaling in the project settings. Clip level scaling types can be altered in the inspector on the edit page.

So you don't need any color management setup in order to make it work. In fact other issues might arise with project wide Color Managed setups if you want to use Fusion.

You might be on to something there, indeed when I switch interpolation the 'black hole' differs in size, where 'nearest neighbor' has only the core of the sun black (in my case it's the sun causing problems).

If I could manage to convert the *.hdr file to an EXR with a brightness limit I could solve the problem. If I find that workaround I'll let it know.

This also explains why with certain locally adaptive grade functions the black hole gets larger, as the false value gets probably smeared more over the image.

I was told this issue is related to the filtering applied on the linear source. I was also told that filtering should be applied in gamma/log. Not sure how true this is, but there is clearly a scaling problem with linear footage in Resolve. The problem is that scaling (and hence, filtering) is processed before grading and not after. This is not a really a bug, though.

As a workaround, you can use a Color Transform or ACES Transform node in Fusion to convert from linear to gamma/log. The reason why this works is that Fusion is processed before everything else.

This way, the processing looks like this:

Source (linear) -> Fusion transform (gamma/log) -> Davinci scale (gamma/log) -> Davinci grade (whatever is your final colorspace).

Should work with HDR workflows, but I never tested it.