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  • Log-Rec709 roundtrip in After Effects

  • Roei Tzoref

    April 28, 2021 at 8:42 pm

    I have been trying different workflows for a while, and have a few insights about this but would like to ask you folks How do you approach compositing LOG mixed with different sources of video with the intention of reverting to LOG composite at the end non-destructively?

    simple setup: got a Log captured footage (Arri) and I want to composite on top of with with mixed elements from sRGB sources (Solid BG with gradient, Video captured sRGB/Rec709 etc) and at the end to export Log.

    so far I tried different workflows and most of them did damage the video signal slightly even when in 32bits:
    1. ICC profiles in After effects using color management: when using color management either through the interpret footage and render dialogs or through color profile converter – the signal does not look the same when completing the round trip. it’s a little clipped. this is not good.

    2. Adjustment Guide Layer with LUT on top of everything and adjusting all my sRGB sources to look like LOG proved very unintuitive. imagine wanting a specific color in the background and have to color correct it under an adjustment LUT to make it look the way you want. and also color correct every sRGB footage from explosions to tv screens to have the LOG look… don’t like that yet this a common workflow

    3. The ACES route: unfortunately I haven’t found a tutorial or a guide to show how to you complete the roundtrip back to LOG. all I have seen is how ACES gives you better color corrections and effects when placed in the sandwich of the Aces adjustments. but not way back to LOG country which I have seen

    4. Invert LUT on sRGB media: the only workflow I found which is non-destructive for now is use an variation of #2 but instead of manually applying color corrections to the sRGB sources to look like LOG, I place on each of them an inverted LUT using OpenColorIO plugin (chose the Arri LUT, then hit Invert).

    please those who have experience with this, share your thoughts and workflows 🙂 thanks

  • Brendon Murphy

    April 29, 2021 at 2:04 am

    I’m a proponent of putting your log source into a linear space using OCIO in-comp (not color management). Then all of your sRGB elements can be converted or graded to something closer to linear, which is less of a stretch than trying to make them look log. Round trip everything back to log at the end with an adjustment layer at the top of comp. Of course, you can always check things under your LUT before rendering.

  • Roei Tzoref

    April 29, 2021 at 6:35 am

    that would be great. I would prefer to bring my LOG to linear. but how do I revert it back to LOG?. how would you do it non-destructively? can you give an example of a basic setup?

  • Brendon Murphy

    May 1, 2021 at 2:46 am

    Roei,

    It’s definitely tough to find good info on this since many Vfx houses develop proprietary workflows to suit their specific pipeline needs. That said, here’s a video that should give you a good idea of how to move forward:

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  • Roei Tzoref

    May 1, 2021 at 3:31 pm

    Thanks Brendon. I actually watched that tutorial before and even when it came out but couldn’t really make it work, but now it works. I still have some questions:

    1. compositing sRGB/Rec709 footage/graphics: I see I should place OCIO plugin on each asset coming from sRGB/Rec709 sources. should I place generic->sRGB texture? I see it works fine on footage. I also see I have utility->curve->sRGB/Rec709. what do you use when you composite each sRGB/Rec709 source that doesn’t have a camera profile? what do I place on solid graphics (shapes/solids)?

    2. I was looking for a way to use Ae’s color management combined with Aces and save all the “preserve RGB” ticks. like explained here in 23:00 https://www.youtube.com/watch?v=7uY4-bPvRKs&t=1610s do you think this is possible?

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  • Brendon Murphy

    May 1, 2021 at 3:41 pm

    Interesting – I have never noticed the issue with Lumetri scopes. For compositing I tend to rely more on the info tool.

  • Roei Tzoref

    May 1, 2021 at 3:51 pm

    sorry I edited my reply. please read it again. the scopes seems to work fine now maybe it was a refresh issue. I will have to run some tests.

  • Roei Tzoref

    May 2, 2021 at 7:35 am

    after discussing with Jacob for a while I figured out some things for the workflow and plan to create a tutorial about my particular struggle with this. thanks for the help Brendon, I appreciate it.

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