ArriRaw (arx) to ACEScg or ACEScct? And no-conversion?

Hey Gang,

Sorta new around here, so hello and I freakin’ love this place. Granted, I feel well out of my depth with an awful lot of what is being discussed here so hopeful and confident someone can guide me a wee bit.

I’m effectively trying to manage a simple workflow working from ArriRaw (.arx) masters and really, at this point, want to be able to perform my comp work (in ACES) and simply render back out, converting to 16-Bit EXRs, with no colour transforms by the time it reaches the grade, and of course wanting to be able to view that final render colourspace before I’ve exported.

As it stands I am using the ACES1.1 Default setup (
I’ve added the additional input rule to read all .arx files with a colour space of LogC/AWG)
Auto converting my media ICS LogC (v3-EI800) / AlexaWideGamut
to WS - ACEScct

However, I’m confident the transform isn’t working for me as when I bypass my input rule my image doesn’t look as i’d expect it, with a much more contrasting image. Certainly compared to when I simply tag the .arx files as Unknown or as Camera>ARRI>LogC/AWG

If someone could point me in the right direction that would be grand!

Thanks kindly and much love x

For comp work you should use ACEScg, not ACEScct. Both have same primaries, but with linear gamma for ACEScg, and some type of log function for ACEScct. Colorist would convert your resulted EXRs to ACEScct for grade.

As for contrast, it`s hard to tell without seeing what happens, but most likely it came from ACES look (its a part of proper ACES workflow), this would not be baked to final results.

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Auto Convert = bad.

Tag only = good!

Share a screen grab of your round trip and we’ll be able to help. This is a pretty straightforward transform.

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Oh, and by the way…please pardon my manners…

Welcome!!!

Bypassing your Input Rule will be definition change the way your image looks! So, that’s expected. Shameless Logik plug…check out my 8 Minute ACES vid. It doesn’t cover your explicit transform but it should fill in some gaps. Also, download the ACES test images and you’ll be able to round trip and have some confidence that your setup works.

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If you are round-tripping back to LogC and only have LogC footage then skip ACES entirely. Use input transforms to go from LogC to SceneLinear Alexa Wide Gamut and then the inverse of that.

I love ACES, but the Arri color spaces are just as good and you won’t be shifting your primaries around.

Add the viewing rule Cameras > Arri > Alexa Rendering and set it to “any scene linear or log”.

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When I worked recently with .arx camera material I choose in the camera settings for Colour Space “Scene Linear ACES”.

And then in the flame Colour Management I tagged the material as ACES2065-1 to get the proper view transform.

Then before comping I put in my batch setups a Colour Management Input Transform set to AcesCG
(Input Colour Space: ACES2065-1, Working Space: AcesCG)

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Thanks everyone for your responses and for helping clarifying the issues!
I’ll follow the working via LogC to SceneLinear AWG workflow, as it suits my simple colour science mind.
Played around with it and happy enough with what it’s doing for me.

Thanks once again. Very much appreciated

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@Beren The bullet proof way is to “only” tag the arri files as ‘logC/AWG’, then make sure your project is set to ACES and the viewing rules will make the picture look ‘normal’. At the batch comp point I would then do a “input transform” to the file (from LogC to ACEScg)… then comp… then “input transform” (from ACEScg to LogC) the pictures back just before the render node. You can then hand over LogC files (EXR,4444XQ etc etc) to the colourist.

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