OCIO and Filmic LUT notes
Last update: 03/29/2020
(image source: courtesy of CreativeShrimp)
Filmic Blender was created by Troy Sobotka, an industry professional and camera enthusiast who saw the problem in Blender and wanted to fix it. So he coded Filmic Blender - a similar color management configuration to ACES, which is the industry standard for VFX.
As I start incorporating ACES into the workflow, I don’t think I need to put the blender filmic on top of it.
Filmic LUT is getting some heated discussions lately on forums. One of the threads that has some great insight is this one.
After reading through all the posts, I tested some of the OCIO configs and LUTs to try out implementing a proper way of doing viewer transform for my daily lookdev/lighting.
The data set I have tested are:
1) Sharktacos OCIO config
2) Sony’s OpenColorIO config
3) Filmlic blener OCIO config
4)looksThe good LUT converted by Recon442
The basic idea is that I can view 3D output in Maya with proper s-shaped curve as the viewer transform (as described in Jeremy Selan’s Cinematic Color paper) in ex. VRay frame buffer during lookdev or lighting and can reproduce the same result in Nuke.
Here is what I found after testing those OCIO configs and LUT.
Sharktacos OCIO config (download link)
Based on spi-anim-ocio, more info can be found here http://docs.sharktacos.com/photography/color-grade.html.
It has these LUTs as below and tells you how to make your own LUT and add it to the config.ocio.
Anim The vd16 color space from spi-anim. See above for details.
vfxVD The vd16 color space from spi-vfx. In comparison to spi-anim vd16, spi-vfx vd16 has a slightly stronger contrast curve, and perhaps most significantly will clip whites above 64 (in contrast with spi-anim which clips them at 4.3) leaving more room for high-end rolloff.
AnimCC The spi-anim vd16 color space with a CDL "look" file applied to it.
AnimLUT The spi-anim vd16 color space with a LUT "look" file applied to it.
vfxCC The spi-vfx vd16 color space with a CDL "look" file applied to it.
vfxLUT The spi-vfx vd16 color space with a LUT "look" file applied to it.
sRGB The standard 2.2 gamma curve from Nuke.
rec709 is the standard rec709 curve from Nuke.
Everything works between Maya (VFB) and Nuke and the result is consistent between the two. In ARV, I only see Anim, vfxVD, Log, and Raw. Hence not that useful if using Arnold. I found the Anim, vfxVD, and rec709 could be useful for my daily lookdev/lighting. Good thing is it comes with sRGB as one of the look so I can quickly flip between sRGB and other looks to compare.
Note that sharktacos OCIO is best compatible with VFB. When using it in Maya’s preference (ex. for Arnold), I don’t see as many looks available as in VFB.intobeing, providesfewerresults
Sony OCIO config
The result is consistent between Maya (VFB & ARV) and Nuke. I get Film, Log, and Raw in both VFB and ARV. A little thing that bugs me is that there is no sRGB LUT for me to quickly flip between sRGB and filmic s-curve for comparison. In Maya, if it is VFB, a workaround is turning off OCIO, and turning on VFB’s sRGB button (when using OCIO, the VFB sRGB button needs to be OFF). But no workaround in Nuke to flip between sRGB and one of OCIO looks when using SPI OCIO configs.
Blender Filmic
The result is consistent between Maya (VFB & ARV) and Nuke. Note the configurations are separated in two folders: one for Blender and Maya VRay, the other for Maya general (load in preference to be used for ARV) and Nuke. Note the config file for Maya general only provide 3 options: Filmic Base Contrast, Filmic Medium High Contrast, and sRGB. Still works, just less options.
Note that same with sharktacos OCIO, Blender Filmic is best compatible with VFB. When using it in Maya’s preference (ex. for Arnold), I don’t see as many looks available as in VFB.
Recon442’s LUT
The LUTs work in Maya VFB, but not in Nuke when applied via a Vectorfield node. Somehow, the result in Nuke is too dark. I didn’t spend too much to figure out why. Decided to not spend more time on it as I already have other working solutions.
For the proper way to view the rendering results in Nuke and writing out from Nuke, refer to the guide here http://www.maximeroz.com/filmic-nuke. It can be summarized as the flowchart below. This workflow seems to only work with Filmic Blender OCIO config. I have experienced different result when implementing this while using sharktacos or spi-anim/vfx OCIO configs.
Conclusion
If I just want to have a proper s-curve LUT to work in Maya for loodev/lighting, it’s fairly easy and straightforward. Pick a OCIO config and write out linear anmatchesexr. Comp and do color corrections in Nuke without worrying about reproducing the s-curve look of Maya frame buffer.
However, if I want to color correct in Nuke while applying a viewer process color transform that match what I have in Maya, then I have to be careful when writing out images from Nuke. Depending on what OCIO config I use, different nodes need to plug in at the end of comp tree to bake the OCIO color transform into the images written out.
In this scenario, sharktacos OCIO config has the flexibility of flipping between sRGB and OCIO looks, as well as the ability to add your own look into the OCIO config easily (i.e. without RnD on how to modify and add your own OCIO looks).
Alternatively, Blender Filmic is easy to use too, providing multiple s-curve LUT with different levels of contrast for users to choose.
If considering the best compatibility among renderers (VRay, Arnold, PRman)
VFB: VRay Frame Buffer
ARV: Arnold Render View
Reference
