Testing ACES LUTs with non-ACES workflow

(JerryHookins) #1

Greetings,

I am currently testing the ACES LUTs which, as far as I understood, they are able to emulate the ACES workflow (LUT’s that emulate the ACES workflow). In this way, a single LUT will be equivalent to the complete IDT+RRT+ODT workflow. Additionally, some .ctl are provided to create “ad hoc” .cube files (LUT’s that emulate the ACES workflow (repost)
).

Now, my (first) question. How could I check if one of my CTL-generated LUT are correct (i.e.: if it matches the related ACES result) ?
I red many different posts on the argument here, unfortunately I was not able to obtain much. I have found the link to https://github.com/ampas/aces-dev/tree/master/images . I will try to explain my workflow with an example:

  1. I choose the “golden” image: camera/syntheticChart.01.exr;
  2. I generate the LUT from ACESlib.Unity.ctl and apply it to syntheticChart.01.exr ;
  3. I compare the resulting image w.r.t. the ACES/syntheticChart.01.exr .

Is my workflow correct? In this case, Did I reproduce only the Input Device Transformation (IDT) part of the ACES workflow or the whole one ( IDT+RRT+ODT)?

I got confused also because I have found the following repo: https://github.com/ampas/aces-dev/tree/master/transforms/ctl which I am not sure how to connected (or use) together with my workflow.

With my best Regards,
JH

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(Geoff Boyle) #2

I tested by using Lattice and measuring the results from different approached to see is they matched.
It wasn’t terribly scientific but it was what got me started.
I also used split screens of rendered images.
https://cinematography.net/ACES-Test-low-budget.html
I’ve also been experimenting with some new ones that seem to work :slight_smile: but bear in mind, these are all meant for monitoring onset in less than ideal conditions and are not meant as LUT’s to be used in any way in a final finishing process.
However, I have tried shooting a series of charts and scenes and putting the rushes through Resolve in ACES into one input of my CG318 and had the output of the camera of the same shot with the LUT applied fed in to input 2 of the monitor and switched between them rapidly.
They look the same to me :slight_smile:
https://cmltests.net/ACES-LUTS.html

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(Nick Shaw) #3

I’m slightly confused what your aim is. The Unity CTL file is, as the name implies, a transform which does nothing. Open the file in a text editor, and you will see it says “Output is the same as input”.

To create a LUT which combines an IDT, the RRT and an ODT into one LUT, you need to apply a series of CTL files. I detail it in the original post – LUT's that emulate the ACES workflow

With the latest Resolve you can build a LUT easily using the OFX ACES Transform. You use a non ACES project, apply the ACES Transform effect and choose your input and output transforms from the drop-downs. Then export the grade as a LUT.

If you need to include full <> legal scaling (as described in my original post) before or after the transform before exporting the LUT, you can use the attached CDL files (they are CDL, but I had to change the extension to .ctl so ACES Central would allow me to upload them. You need to change it back.)

full_legal.ctl (398 Bytes)
legal_full.ctl (400 Bytes)

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(Paul Dore) #4

A wider variety of ACES LUTS can be exported using the ACES 1.1 OFX Plugin. There’s no need to open a new project, just add it to any node, export the required LUTs, then remove it if no longer needed.

ACES 1.1 OFX Plugin

ACES 1.1 OFX Source

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