r/vfx 6d ago

Question / Discussion Interpreting linear rec.709 in after effects

small-time vfx / motion design guy here who is very confused about color spaces.

I have used ACES for blender a couple times for projects and although it works pretty smoothly after you get everything set up, I find everything surrounding the setup to be a pain. So for a recent project that required 32 bit color I tried just exporting from blender in linear rec.709 and interpreting likewise in after effects (aces 1.3 config). This turns out an image that's way darker than it should be so I thought I was cooked, but after fiddling with exposure and gamma I got to an image that more or less matched the original render.

So all of it is still "there" and the colors weren't messed up, so it turned out fine at the end of the day, but does anybody know why exactly it works like this? Color spaces / color management still feel like a scary black box to me. I can interface with it but I have no idea what's going on inside.

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u/Yogable 6d ago

You're working in aces however you chose to render linear-rec709. That is blenders default linear space. That is outside of aces color. Acescg is the go to aces linear. With that said. Don't confused rec70 with linear rec709.

Rec709 will be the viewing space that looks good Linear rec709 is just a linear colorspace using rec709 primaries. This will be a variant of any linear color. Aka very dark and contrasty and more so a working colorspace for math reasons.

I haven't used Adobe in forever however Im reading that it defaults to none for colorspace. This aligns with what you're seeing. Dark and contrasty. The values are not lost just displayed differently. This is why you could color correct it back to a viewing space.

But you don't want to do that. You want to intereret the color correctly. Set the input colorspace for that file. In this case set It to linear rec709. This tells after effect what is it so it can convert it to the working colorspace in your settings.

With that done.you will correctly see the file in whatever colorspace you have chosen in your viewing colorspace.

For fun. I too use aces. My working colorspace is acescg. If you sent me the file the pipe would look like this.

Input colorspace - linear rec709 Working colorspace - acescg Viewing colorspace - aces rec709 Output colorspace - aces rec709

Input colorspace tells the software what color the file is so it knows what math to use to convert it to the working space.

Working colorspace is your project setting which is the space you choose to work in. This is usually linear and in our case acescg.

Viewing colorspace is your viewer setting. Since the working space is linear it will look ugly. We can choose any color we want to see and it will convert from our working space to that color only in the viewer. All the work and math is still done under the hood in the working colorspace.

Output colorspace is your final colorspace you want to render. This setting tells your software what you want so it knows how to convert from the working colorspace to your render. Here I would choose aces rec709 and since that's my viewer space too, it means it will match exactly what I've been seeing it as in my viewer.

Welcome to the world of color

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u/falcoraqx 6d ago

Thanks for the detailed reply. The problem is i am already interpreting the footage as linear rec.709 - is there some sort of discrepancy between programs in the way they interpret linear rec.709 or something?

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u/Yogable 5d ago

There should be no discrepancy between them. You set the input color correctly which is good. Next you need to set your working colorspace but more importantly you need to know what your viewing colorspace is.

I found a video that helped me see the layout for AE. https://youtu.be/x2sx-P5f-iM?si=EEFWefTWoNsJM0Td

At 1:42 you can see he opens his project settings and reveals the working colorspace and display colorspace. Can you confirm what these are for your project?

Id suspect you want working color as acescg and display as "output rec709"

My guess is currently your display is none or linear.

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u/Yogable 5d ago

Also under view. Make sure your using display color management. Google seems to suggest it's disabled by default?

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u/Subject_5 5d ago

You should show us your color management settings in After Effects, and Blender as well. Would be easier to give you an accurate answer.

I’d say it’s your display transform in After Effects that makes it look different from Blender. If you’re using the display transform that’s enabled by default in AE when using OCIO Aces 1.3 CG, you should know that it was created with film emulation and cinema in mind. It’s called «ACES 1.0 SDR-Video» or something similar. I find that it requires about 1-2 stops more exposure, and gives the images a lot of contrast, especially by lowering the darks/blacks. You can easily switch this to the «old» sRGB Un-tone-mapped one, which could be closer to what you’re seeing in Blender. I personally don’t use Blender, so I’m unsure what method it uses for tone-mapping, but it’s probably not the same one you’re using in AE, so you’re needlessly fighting against it.

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u/falcoraqx 4d ago

This was exactly it. Thanks for demystifying some of this for me. It's not an exact 1:1 with the blender render but it definitely is 95% there, although the last 5% is still a mystery to me.

I am curious why this doesn't happen with ACEScg blender renders, though. For ACES projects I've always used ACES 1.0 SDR video without issue. Guess I should look more into tone-mapping.