Bake ACES info ito EXR

[hermit.crab]

There should be no additional curve in PS. Its workging if i save the sRGB EXR (non OCIO).
I agree its looking correct in Chaosplayer.

Well, PS has its own color profile. Does the image get fixed if you apply a reverse gamma (.4545) Exposure layer?

[oglu]

The image gets only fixed if i turn on "convert to working color space" in PS.
And thats exactly what i dont want. But i fear thats how it is for now.

[mschreck]

I am having the same problem with vray baked color transforms to photoshop workflow with (multichannel) exr.
Any ideas what the best workaround is nowadays? roundtrip through nuke?

[piotrus3333]

If you are using 32bit psd file there is no way to turn off srgb transfer function “view lut”. every icc color profile assigned to this file is linearised by default. no way around it
you can use “soft proof” view with your monitor profile to see the exr in PS without any transform but then you are limited to 8bit export with “convert to srgb” option off. if you convert psd file to 8 or 16 the “view lut” gets baked.

if you are saving display reffered output into exr you can probably go 32float and bake additional inversed Photoshop’s view lut.

do you really need 32bit psd?

[mschreck]

honestly i am a real photoshop noob - usually we work in nuke.But on this project we need the renders to go through Photoshop.We would like to use multichannel exr and use EXR IO for import.
The resulting PS document is a *32bit Document even though i have set the vray image format option to 16 bits (half float)

[piotrus3333]

Krita would be a solution as I assume you go back to Nuke after Photoshop? and Photoshop is there just for some paintovers?
it has ocio v2 support (view lut only, cant bake the transforms) and icc profiles are working ok with floating point images.
it reads multichanel exrs although not multipart exrs. might be a deal breaker.

Photoshop is using 32bit psd file for any float data, full and half.
If you use half float for your display transformed output exr are you sure you have enough color information there? midtonnes to highlights this is like 10bit file precision. might be enough for what you need I guess

if I do Photoshop with float color I just use big csp luts that account for “srgb view lut” in photoshop. I get 1:1 when compared with proper ocio transforms.

[mschreck]

The files will be further processed in after effects after matte paint.10bit should be enough for our use case but we need the initial Color range to have the flexibility before going further down the pipeline reducing the documents Color depth.what are cps luts? I was thinking that it might be possible to create a lut layer to match the colors as a first step in photoshop.
i will look into ocio and icc profiles,just want to make the workflow for matte paint as simple as possible,

[piotrus3333]

I have no experience creating more custom icc profiles but from discussion at ACES Central I remember one of the mentioned workflows was getting 16 bit integer log encoded files (acescc or acescct I guess) for matte painting to PS with icc profile as ACES display transform. Not sure how much matte painters like painting in log (I don't think PS color picker is color managed)

csp luts are the only lut types working in PS that can access floating point range of colors. 1D prelut is max 4096 points + size 65 3D cube. it is enough to perfectly encode ACEScg into ARRI LogC4 (range -0.018... to ~470 float, ACEScc log is maxed at ~222 float at 1.0).

attached: lut - aces 1.3 acescg to aces srgb display with reference gamut compression + reversed srgb transfer function to get rid of Photoshops view lut: https://youtu.be/6zbHbYmhDvQ

a thing to consider is 32bit psb file inside 16bit integer psd file as smart object (more options for painting/editing).

[mschreck]

Man, thanks for the detailed info.i will pass it on to our TDs hoping they cane make sense of it really appreciate this.i will update what we will end up with.
have a nice evening

[oglu]

I use brute force bake ACES into the EXR. No special setup needed. But i dont recommend the workflow if you dont know what you are "not" doing.

[oglu]

I did a fast tutorial.
https://youtu.be/7J1XBvx6iDA

[piotrus3333]

I use brute force bake ACES into the EXR. No special setup needed. But i dont recommend the workflow if you dont know what you are "not" doing.

issue with baking ACES ocio transform from VRay is that you need custom ocio config to get ACES 1.3 version of the transform (one with Look: Reference gamut compression) as ocio looks are not supported by VRay's frame buffer.

edit: VFB: looks from ocio configs - Chaos Forums

[oglu]

As i mentioned above its not a recommended workflow. But its close enough to work with for what i do.

[mschreck]

Thanks for the suggestion - unfortunately going 8bit is not an option in our use case.I will test the lut aproach now.

[mschreck]

The csp is looking very promising i still have a slight color shift (too much red) in my image, i guess because i use slightly different settings in maya vray

but the aproach seams to be the right solution.