OCIO Context

OCIO Context loads an OpenColorIO config into Radiance's shared OCIO manager for the session. After it runs, every Radiance node that does colour work - Color Space Convert, the OCIO-aware entries on Read's color_space menu, anything asking for a colours-pace name or alias - resolves names against your config instead of OpenColorIO's built-in default. You set it once per session and then stop thinking about it.

Why that matters: colour-space names are config-specific. ACEScg means one thing in an ACES studio config and something subtly different in a show config with a custom working space, and names that exist in a studio config - a particular camera log, a show LUT's input space - simply don't exist in the default. Handing the manager the real config is the difference between "the transform you asked for" and "OpenColorIO guessed". The KB's post-processing.md is blunt that this whole layer is nearly absent from community discussion and that a single un-managed decode poisons a comp - that's the failure this node prevents.

What it does, exactly

One input. config_path points at a config.ocio file, and the default in the box - C:/ACES/config.ocio - is a Windows ACES convention, so if that isn't you, change it. A relative path is resolved by looking in ComfyUI's input/ folder first, then output/, which is a nice touch: drop a config.ocio next to your inputs and point at config.ocio.

The output is ocio_context, typed RADIANCE_OCIO. It carries the loaded config (path and name). Wire it into Color Space Convert and that node is guaranteed to run after this one - that's the actual reason the output exists, ordering, since ComfyUI has no other way to express "load the config first".

Two things about this node from version 3.5.0 are worth knowing if you're reading old guides. First, it's now an output node, so it runs whenever it's in the graph - before that change nothing consumed its output, so ComfyUI never executed it and the config was never loaded. Second, a config that fails to load is now a hard error rather than a status string nobody read; the old working_space widget, which was stored and never used, is gone. Saved graphs still sending it are handled silently.

Install

Radiance installs through ComfyUI Manager - search Radiance, install, restart, refresh - or manually:

cd ComfyUI/custom_nodes
git clone https://github.com/fxtd-studios/radiance.git
cd radiance
python -m pip install -r requirements.txt

You need the PyOpenColorIO binding, which opencolorio in requirements.txt provides; Manager's post-install script checks for it and installs it if missing. Without it this node raises rather than silently doing nothing. You do not need to install a config - Radiance falls back to OpenColorIO's built-in ACES 2.0 studio config at startup, and honours $OCIO if you've set it, so a lot of people never touch this node at all.

Set RADIANCE_ALLOW_DOWNLOADS=0 before starting ComfyUI if you want zero automatic downloads anywhere in the pack.

Where people get burned

• Path escaping the input folder. A relative path is looked up in input/ then output/ and nowhere else. If your config lives elsewhere, give an absolute path.
• One shared manager. The config you load replaces the session-wide one until another is loaded. If you're running two graphs that want different configs in one ComfyUI session, you're going to have a bad time - pick one.
• Backslashes on Linux. The default is a Windows path. Copy-pasting a folder path from Explorer into a Linux box gives you a config that never loads, and the error is about the file, not the slashes.
• A show config with no ACES names. That's not a bug. Your config defines what names exist; ask OCIO List Colorspaces when you're not sure.