re: ProRes 4444 -- after FX, luminance changes

We have a commercial shot on the Arri Alexa, coming out as ProRes 4444 clips. The offline was simple, editing in ProRes 4444, and then the clips were colour-corrected by a post facility (who also did the DMT copy/backup work on set) and re-rendered out as ProRes 4444 clips from a Da Vinci Resolve.

But, after we send those clips to an FX artist for some rotoscoping work, the clips are coming back significantly darker. I believe he's using Adobe After Effects.

Can anybody tell me what the culprit might be? The FX artist thinks it's because he's using ProRes 4444 source clips but he doesn't have ProRes 4444, so he's rendering the FX clips out as ProRes 422 HQ. I found a download link for ProRes 4444. But, I don't think that discrepancy causes luminance shifts. (I tried sticking a ProRes 4444 clip into a ProRes 422 HQ timeline to simulate the issue, and saw no shifts.) Or am I wrong?

I also pointed out the old Mac vs. video gamma issue (1.8 vs. 2.2). Is there a setting in After Effects that affects colour profiles and gamma settings?

Aside from these, what else can he check to locate the cause of this issue?

It's also curious that we've worked with this FX artist for years, using Uncompressed 8-bit and 10-bit HD and also ProRes 4444 in one case, and we've never had this issue before, which leads me to believe he does know correct settings for rendering. Is there a quirk with Alexa-originated clips we're missing?

Software:
Mac OS 10.6.8
Final Cut Pro 7.0.3

Media settings:
ProRes 4444
1920x1080
23.98fps


www.derekmok.com

Or could it be to do with the fact that he's possibly taking in 4444, which is seen as RGB in AE, then exporting as 422, which (I'm right on the edge of my limited knowledge space here) is Y'CrCb?

Thanks for the suggestion, Jude. If that is the issue, that means I was wrong and the FX artist did not get ProRes 4444 from us in those past jobs.


www.derekmok.com

>Is there a setting in After Effects that affects colour profiles and gamma settings?

Yes.

[help.adobe.com]

As always when working with different platforms, interpret the color profile of the source files, specify color profile of composition (project working space in After Effects), then assign a color profile on output if required. Do a test to make sure the softwares are set up correctly.



www.strypesinpost.com

Do I need to set Sequence video processing to 8-bit? I haven't seen the 10-bit vs. 8-bit issue result in darkening, but I'm really not an expert at the nitty-gritties of video technology.


www.derekmok.com

>Do I need to set Sequence video processing to 8-bit?

No. Keep everything at high precision YUV in FCP, if possible, but this shouldn't matter unless you have added effects in FCP and you're finishing in FCP.

First, check to see which software he is using (and also version number), and if he is converting to any formats along the way. And contrary to common practice, for graphics work, files should never be converted to animation or none. Does he have FCP, FCP X or Motion installed?

If he is working in After Effects, make sure he interprets the footage as REC 709, and set project working space to REC 709, and he exports directly to ProRes 4444 or ProRes HQ.

I don't think he tweaked a setting this time. Most people don't notice and don't know that video always has a gamma curve applied. And because most people don't do roto or DI work, they don't ever notice the gamma shifts that QT is quite notorious for.



www.strypesinpost.com