◎ Radiance Blend Composite

Stock ComfyUI lets you paste one image over another, but the built-in compositing can flatten your values to 8-bit on the way through. That's the whole pitch of Radiance Blend Composite: it composites in 32-bit float, so if your base or blend layer is carrying HDR values above 1.0 - scene-linear EXR footage, a bloom pass, anything you've been feeding through Radiance's float pipeline - they survive the operation instead of clipping to white.

It's a two-layer compositor, nothing more. You feed a base (bottom, background) and a blend (top, foreground) image, pick a mode, and set how strongly the top layer shows through. Eight modes: Normal, Add, Screen, Multiply, Overlay, Soft Light, Difference, and Divide. That's the classic Photoshop/SVG set minus the exotics, which is exactly what you want when the job is "stack a light pass on a base" or "screen a bloom back in" without installing a whole image-ops suite.

What actually matters

Three inputs, and only three:

• mode - the blend operation. For HDR work, Add and Screen are the ones that preserve highlights; Multiply and Divide are how you'd do a crude light/shadow pass. Normal is just alpha compositing.
• opacity - 0 to 1, overall strength of the blend layer. Start at 1, back it off if the effect is hammering the base.
• mask - optional grayscale mask. White = full blend, black = base only. This is your per-pixel control: mask in a reflection, keep a face clear of the texture pass, that sort of thing.

The node resizes the blend to match the base automatically (it interpolates if the layers differ in dimensions), which saves you a Resize node and one of the classic "why is nothing compositing" failures.

Output is a single image, wired straight into whatever comes next - a grade, a save, or back into another composite if you're stacking layers.

The honest caveat

Radiance's whole marketing is the 32-bit pipeline, and the community's reaction to that claim was skeptical - the launch thread had people pointing out that plenty of nodes in the pack quietly drop to 8-bit integer precision mid-pipeline. This node is one of the ones that mostly lives up to the pitch: the blend math runs in float32, and Add/Screen keep HDR values intact. But the output only stays HDR if what went in was HDR. Feed it an 8-bit PNG and it's an 8-bit result, no magic. For genuinely HDR compositing you want EXR or scene-linear inputs upstream.

Install

Same as every Radiance node - it ships in the pack:

cd ComfyUI/custom_nodes
git clone https://github.com/fxtdstudios/radiance.git
cd radiance
pip install -r requirements_linux.txt   # or requirements_windows.txt / requirements_mac_silicon.txt

Or just search "Radiance" in ComfyUI Manager and click Install, then restart. If Manager refuses on security level, clone manually - the README calls that out specifically. Linux users need libopenexr-dev installed before the pip step (the pack's OpenEXR dependency won't compile without it).

The install is heavy - OpenEXR, OpenColorIO, colour-science, transformers, imageio-ffmpeg - so the first launch is slow. If another pack conflicts on a shared dependency, reinstall Radiance's requirements last and restart.