Importing Open EXR files

[JBuon]

Hello all,

I’m comping a woman onto a background. The womans plate is log, the background is an open exr file. I need to send over a comp in log for the colorist to grade. How do I tag the open exr?

Thanks in advance!

[GPM]

Welcome James! And I am of zero help here. My answer to maddening color management issues is, just work in rec709. The rest is nonsense.

[randy]

Ignore @GPM. He came with the place.

So, you’re going to need to dig. What kind of log? And what kind of OpenEXR did you get? You’re going to need to ask whomever gave it to you what they are so you can tag appropriately.

[GPM]

Just ask for a rec709 ProRes 422. Done and done.

[JBuon]

I think I may have sorted it out actually - the plate is ProRes4444 and the EXR I’m told is SRGB 32 bit float.

I did a view transform on the EXR stuff and set it to “lin to log” and I think it looks right?

[JBuon]

You know that shit won’t fly with these CG dudes

[GPM]

I’m just playing. This stuff is fortunately just out of my wheelhouse.

[randy]

Nope. Not enough details. I mean, you could be right, but, you could be wrong.

You’re going to need to know what precisely to tag the EXR and the 4444. The 4444 could be SLog, RWG, Alexa Wide Gamut, etc. The EXR could be Scene Linear / Rec 709, Scene Linear / sRGB, Scene Linear / AWG, etc etc.

The tag is typically includes 2 pieces of info…a gamma curve and a color gamut. Without both pieces you are going to have a bad time.

[JBuon]

Copy that. I’m lacking a lot of info on my part regarding color management as a whole.

I’m being told the EXR is linear, and the ProRes is AlexaV3LogC

[ytf]

Once Randy figures it out, you should do a round robin with the cgi dudes to make sure everyone is on the same page before any work gets wasted.

[JBuon]

I like the way you think

[randy]

Linear isn’t enough information. You need a gamut as well. A gamut is all the potential colors your image might be. That’s either Rec 709, sRGB, Alexa Wide Gamut, etc.

Linear refers to light. Gamut refers to color. You need to know both.

[JBuon]

The EXR is Linear sRGB

[randy]

Use this for the scene linear sRGB.

Use this for the 4444

When done do this…

[randy]

Then do this

[space_monkey]

Just convert the Slinear sRgb to Alexa and comp it in Log no reason to add the extra steps of aces imho.

[JBuon]

Thanks Randy, this was a huge help!

[andy_dill]

@JBuon

I’m being told the EXR is linear,

I hear this a lot and it always drives me bonkers. As Randy said, that’s not enough information and it always seems that getting MORE info involves pulling teeth (out of a head that wasn’t aware that teeth even existed, or something). I should really look into what “lazy CG linear” is these days so I can just auto-translate that and not have to have the following conversation:

“it’s linear”
“what kind of linear?”
“just linear.”
“Do you know the gamut?”
“the gamma is 1”

[cnoellert]

“Lazy CG linear” is whatever the default is in a Nuke read node. Most of them have never bothered to investigate.

[Stefan]

I think it’s safe to say that 99% of the time, linear from CG (or anything not from a camera) will be either rec709/sRGB or ACEScg (AP1) primaries, right?
Then yes, we sometimes get camera files shot in linear wide gamut, but most of the time they are either log or display referred, (mostly video709, all the RED annoying variances, or phantom kinda video709 for the display referred stuff)
rec709 and sRGB primaries (gamut) are the same btw.