Odd Gamma on EXR round trip

I was just working on clip to remove some blemishes with the paint tool, something that I’ve done countless times. This time the round trip app sequence is slightly different and I’m running into a weird gamma shift that makes the replacement clip significantly darker.

The clip is from a Panasonic Varicam in V-Log. The edit is in Avid. I exported the clip from Avid as an EXR sequence with all color adapters disabled. In Silhouette I’m seeing the normal low-contrast log image, work on it, and then export it via an Output node into a new EXR sequence. Usually that can be imported to replace the original clip and everything matches.

However, in this case today, when I import the EXR sequence either in Resolve or Mistika the resulting import is darker and appears to have regular 2.4 gamma on it. But nothing has been specified during import to do that. There are no LUTs, no IDTs, etc applied.

If I do open the first frame of the rendered sequence in Photoshop, it looks proper in terms of V-Log footage.

So it’s not pixel values, it must be a color space handling issue. I’m assuming that Avid may have added some weird color space identifiers into the files during export. Those don’t appear to affect Silhouette itself or Photoshop, but appear to be picked up by Resolve and Mistika. And would have had to be copied by Silhouette from the source to the destination.

Any ideas???

Thanks,
Jan

Update: Definitely seems to be an Avid problem.

I located the original camera file and created the EXR sequence in Resolve, re-ran the Silhouette paint node over the new source, transcoded the export in Resolve from EXR back to MXF and all was good.

Have to flag that with the Avid folks.

Hi @jan. The linear workflow in Silhouette when using EXRs is completely non-destructive - there are no colorspace conversions at all, so I was going to point finger at Avid. Glad you found the issue!

Jan,

Did you refresh the sequence in Avid before exporting the EXR?
If you select the clip and drop the adapter in source settings you still need to refresh the sequence.
Likewise, selecting the sequence and remove color adapters does not take it off entirely!
Could be the cause of your issue.

Brian,

Yes, I did. It didn’t make any difference though.

I’ve been a bit spoiled by Resolve and EXR, which is super easy to export and re-import reliably and without having to worry about color space information. I think Resolve actually does a linear CST upon export/import automatically.

My take away is that I have to be more mindful how the various platforms handle color space with EXR. Also, you may have to be explicit to convert it to ACEScg or something similar, or at least export/import in the same app. In this case I crossed apps, which was in hindsight unwise.

I’m happy that Avid finally supports both export/import of EXR without expensive plugins, though I’ve had some bugs on the import, where it would drop the last frame for some reason.

Thanks for the reminder on the Avid tricks though.

Jan