Ari to ACES EXR's misunderstanding


(Mel Massadian) #1

Hello Everyone,

First time I’m trying to do a full ACES pipeline but I’m having some issue and I think misconceptions.

I did the conform of the editing using the source ari files.
I then used ARC_CMD to convert the editing shots to ACES Compliant EXR’s.

In what colorspace are they now ? ACEScc ? ACES2065 ?

The idea is to work in Nuke after which I know by default is using the ACEScg colorspace.

In order to keep my source intact after VFX what is the right output space to put in the write node for grading delivery?

Thanks


(Joseph Goldstone) #2

They are in ACES (SMPTE ST 2065-1:201whatever)

Also the files conform to the ACES container spec (SMPTE ST 2065-4:2013).


(Mel Massadian) #3

Thanks for the reply.
So is it right that when we say ACEScc to ACES it actually means ACEScc to ACES2065(whatever) ? right ?

I’m planning on making a guide as I think some part of the pipeline are still a bit hard to grasp with available ressources


(Joseph Goldstone) #4

Just think of the overall project as a framework for image interchange, and ACES as being the Academy-specified color encoding for that interchange. That color encoding is written up in a SMPTE document whose identifier happens to be ST 2065-1. Try googling for “aces 2065-1 SMPTE” and I’m sure you will find the formal document.

There is already an Academy document, carefully written up by Scott Dyer, that details the official names for all the pieces of ACES. Perhaps he or Steve can post a link to it. I think it would help you (and many others).


(Mel Massadian) #5

Thanks Joseph, I really want to embrace ACES.
The main concepts are pretty easy to grasp but confident pipeline integration is another story.
I’d love to read the paper your referring to !
I’m actually going through all ACES Specifications and Technical Bulletins to learn more.

My goal is to mix/match BMC 2.5k (raw dng’s) with an ARRI Alexa Plus 4:3 (raw ari’s).


(Joseph Goldstone) #6

Now that I’m using a device with a real keyboard and can poke around:

go to this page:
http://www.oscars.org/science-technology/aces/aces-documentation

The last item in the section titled “System Documentation” is TB-2014-012, “Academy Color Encoding System (ACES) Version 1.0 Component Names”. That tells you what things are officially called now, but also identifies older names you may come across.

There are no names in the version history nor is there any acknowledgments section but I am pretty sure this was largely or wholly the work of Scott Dyer at the Academy, who deserves a lot of praise for pulling this together.

As for your goal, ACES is a good tool for color matching the output of various cameras. The importance of matching noise characteristics, dynamic range, and so on depends on your content, and in any case is outside the scope of ACES.


(Steve Tobenkin) #7

Thanks Joseph! Appreciate your support.


(Walter Arrighetti) #8

You can also find a review of all ACES-based colour spaces here:

p.s.: It’s not mandatory to pre-emptively convert footage files from their “raw” formats (in your case ARRIRAW) to ACES (OpenEXR as per SMPTE ST2065-4 specs) prior to using an all-ACES workflow – In fact, sometimes this is a cumbersome passage that you only do for additional reasons, but not a choice picked up by itself.


(Mel Massadian) #9

Thanks nice post.

The reason for the conversion :

  • compatibility
  • performance (scanline vs tiled)
  • pre up/down scalings.