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[euge04]

Hello-

I'm having an issue prepping files for VFX artists using Nuke.  I am conforming shots in the Baselight from ProRes4444 files.  I am setting my input format on my clips to Log and my sequence format to Log and exporting DPX files.  When I open up the original Quicktime in Nuke and compare them to the exported DPX files a gamma shift has occurred in the DPX files making them brighter.  I have my colorspace on both the Quicktime and DPX files set to AlexaV3LogC.

I have since attempted to export using Video as my input format and Video as the format for my sequence and I end up with the same result out of the Baselight. 

I did try attaching a Truelight Internal HD cube that comes with the Baselight to the shot itself.  This actually creates a render that closely mimics the Quicktime in Nuke. 

This is a problem because we are not doing the color correct.  I am attempting to re-create the same LogC curve throughout our workflow so that our clients color corrections remain the same.  If anyone has done this workflow I would appreciate it. 

I'm using the Baselight for it's awesome conform functions but this problem is perplexing me greatly. 

Thanks!

[Nick Shaw]

When I open up the original Quicktime in Nuke and compare them to the exported DPX files a gamma shift has occurred in the DPX files making them brighter.

Don't forget Baselight reads ProRes files with the "legal" levels they are internally coded with. Nuke expands them to full range. You need to set "Legal to Full Scale" in the "Video LUT" section of the Baselight render window to get DPX files which will match the QuickTimes in Nuke.

[euge04]

The footage is nearly perfect but we are now seeing a small color shift in the footage.  The DPX files appear slightly less green than the Quicktime.  Have you experienced this problem Nick? 

Thanks again for you help.

[euge04]

Maybe a LUT converting the footage from LogC with legal values to LogC with extended values will prove more accurate?  I'll have to test it in the morning.

[Nick Shaw]

The DPX files appear slightly less green than the Quicktime.  Have you experienced this problem Nick?

Yes I see the same thing. It's part of the joy of QuickTime!

Both Filmlight and The Foundry have had to write their own code to get around some QuickTime limitations. This results in slightly different colour processing.

I'll have to run some tests at some point and try and work out which one is more "correct".

I just did a quick test, using test files that I have as both ARRI RAW and ProRes, and converting the RAW files to DPX in the ARRI RAW Converter gives DPXs which very closely (but not perfectly) match DPXs made in Baselight from the ProRes files. They do not have the green tint present when reading the ProRes directly in Nuke.

[euge04]

Interesting.  I will have to find out what system my client is color correcting with.

The DPX files from the Baselight may prove to be more constant with other systems.  To get the green cast back I tried rendering to ProRes4444 and an Uncompressed YUV 444 codec in the Baselight and they both have the green cast and nearly match the original Quicktimes being used in Nuke since they are coming from Quicktime files.  I'd prefer not to do this of course.

You've been very helpful Nick.  Thanks for your help.