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Clipping when writing to DPX from linear project

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Sean CunninghamClipping when writing to DPX from linear project
by on Apr 29, 2015 at 1:14:49 am

I did search both here and elsewhere online for a solution already discussed but I came up empty handed. We just ran into this issue delivering a handful of shots on a music video and trying various export parameters has so far not solved the issue.

I'm compositing in a 32bit linear project with the sRGB working profile. The client requested 10bit DPX and the first batch of exports were kicked back because the highlights were clipped. Visually, reading them back into After Effects they look fine and match the comp and match the incoming plates. Adjusting exposure revealed that the several extra stops of highlight information in windows, etc. were being clipped off in the export that I could see in the original plates (EXR written from Redcine-X).

I followed the Full Range recommendations that I've read here and elsewhere, setting Units to Decimal. The first time I'd forgotten and left the export profile set to my working profile (sRGB) but setting export to Universal Film Density, setting Preserve RGB, no combination seems to write DPX files that don't come out clipped or otherwise wrong once re-imported or inspected in Nuke. The couple shots a different fellow did in Nuke, using their standard DPX export are fine, which only furthered the anti-AE sentiment coming from that part of the office.

I know it's just an issue with something in the export and something I'm overlooking but this is the first time I've ever even had to think about DPX from AE. We ended up convincing them to just take EXRs so that their color session wasn't held up any further and I could get it worked out for the next time.

What am I overlooking?

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Tudor "Ted" JelescuRe: Clipping when writing to DPX from linear project
by on Apr 29, 2015 at 7:22:00 pm

Not an expert by far in this, but this guy knows what he's talking about and he recommends ProPhoto RGB because it has a larger gamut. Check out his article:

Tudor "Ted" Jelescu
Senior VFX Artist

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Sean CunninghamRe: Clipping when writing to DPX from linear project
by on Apr 30, 2015 at 5:17:27 am

The working space doesn't actually effect the values except for how they're displayed. Setting your working space to a higher gamut setting is/should be more a function of your monitors capabilities. My monitor is rated at 100% sRGB. This is an export problem and not a working space problem.

I know this to be a fact because I can write the comp out as EXR, read it back into After Effects and it still has all the extra stops of detail in the highlights. I can read these EXRs into Nuke and write DPX that read back in and look identical to the EXR while also retaining the extra stops of highlight information that After Effects clips if I write the same comp as DPX.

And today I confirmed that I can read the EXR into Natron, the Open Source Nuke clone, drop a write node, set output space to Cineon and those DPX read back in looking identical to the EXR while retaining the extra stops of highlight information that After Effects is clipping out when I try to write DPX.

I'm going to see if perhaps switching to a workflow that utilizes Fnord's Open Color plugins, rather than relying on Adobe's color management, solves the issue since my understanding is it can be told to process color consistent with Nuke as well.

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