◎ Radiance ARRI Wide Gamut 4

If you've ever been handed an image that came out of a camera and the colors look like they belong in a different universe, this node is why. AWG4 - ARRI Wide Gamut 4 - is the color space of the Alexa 35, ARRI's current flagship sensor. It's wider than Rec.2020, and like every wide-gamut camera space, its raw numbers mean nothing until you convert them somewhere you can actually look at them.

The Radiance ARRI Wide Gamut 4 node is a one-trick pony, and it's a useful trick: it converts to and from AWG4 using baked-in ARRI-specified matrices. No learning curve, no settings beyond a dropdown, one image in, one image out.

The one input

• direction - four choices: AWG4 to ACEScg, ACEScg to AWG4, AWG4 to Linear sRGB, Linear sRGB to AWG4.

That's it. Pick which direction your data flows. The mechanism is a pair of 3×3 matrix multiplies routed through XYZ - AWG4 → XYZ → (your target), or the reverse. It's the same matrix math that lives in Resolve and Nuke's color management, hardcoded per the ARRI published primaries. Reading the source, AWG4_TO_XYZ and its inverse sit right in the class, and the sRGB/AP1 matrices are the shared ones the whole pack uses. Deterministic, instant, GPU-free - this is a lookup-table job, not an AI job.

Where it belongs in a workflow

The realistic scenario: you have an Alexa 35 clip or a plate from a shoot, and you want it in the same working space as your generated content. Run the source through AWG4 to ACEScg and it now lives in the same ACES AP1 space your Radiance chain grades in. When you're done, ACEScg to AWG4 sends it back for the deliverable or for compositing against the original footage.

The less realistic but fun version: take an AI-generated image, convert it into AWG4, then back out through one of Radiance's log curves, and you get that "shot on a cinema camera" round-trip look - mostly because you're moving the data through a much wider gamut than it was born in, which subtly re-weights the channels. It's a parlor trick, but it's a cheap one.

Caveats

• This is a linear conversion. If your camera footage is still in LogC (ARRI's log encoding), run it through the log decode first - the pack has LogC3/LogC4 nodes in the same Radiance/Color menu - or your "linear" input will be log-ish values pretending to be linear and the grade will fight you.
• There's no gamut-mapping fallback here. Out-of-gamut values carry through as negatives or >1.0 floats rather than being rolled off. That's technically correct behavior for a VFX space, but if you're converting to Linear sRGB for a plain PNG, consider clamping or a gamut-compress pass downstream so you don't ship an image that looks fine in the viewer and blows out in a browser.

It's a specialist node. If your life doesn't include camera plates, skip it - the generic ColorSpaceConvert in the same pack also lists ARRI Wide Gamut 4 as a source and target, so you can do the same thing with more options. Reach for this one when you want the camera-specific path with zero decisions.

Install

Same pack, same route - ComfyUI Manager → search Radiance, or manually:

cd ComfyUI/custom_nodes
git clone https://github.com/fxtdstudios/radiance.git
cd radiance
pip install -r requirements.txt

Then restart ComfyUI.