ComfyUI ACES EXR Toolkit

ComfyUI ACES EXR Toolkit

Professional ACES and EXR workflow nodes for ComfyUI.

This extension adds practical OpenEXR loading/saving, ACES Studio 1.3 OCIO color transforms, alpha-aware previews, and simple HDR tone mapping for image pipelines that need float EXR support.

Features

• Multi-Layer EXR Export: Save multi-channel EXRs containing beauty, depth, normal, mask, diffuse, specular, and emission passes into a single file for Nuke/Resolve VFX workflows.
• EXR Layer & Metadata Inspection: Extract named channels/layers from multi-layer EXRs, and read complete header metadata JSON.
• Advanced Tone Mapping: Includes AgX (Blender standard), Filmic, DaVinci, ACES fitted, and Reinhard curves.
• Fast OCIO Processing: Native bulk-pixel processing via PyOpenColorIO for lightning-fast ACES transformations.
• Load EXR Sequences: Auto-detects and loads numbered EXR sequences (render.0001.exr) directly into ComfyUI batch tensors.
• 16-bit & 32-bit Export: Save half-float (16f) or float (32f) EXRs with standard compression codecs (ZIP, PIZ, DWAA) via OpenEXR.
• HDR WebGL Viewer: A GPU-accelerated viewer with real-time Exposure, Gamma, False Color (ARRI-style), and Channel isolation for true 32-bit float inspection inside ComfyUI.
• HDR Generation Tools: Includes Synthetic Highlight Expansion to generate HDR from SDR AI outputs, and Exposure Bracket Merging.
• Path Security Containment: Full containment protecting against path traversal, while supporting custom render drives configured via extra_model_paths.yaml.

Nodes

| Node | Purpose | | --- | --- | | Load EXR | Load .exr files from ComfyUI input, with optional path override | | Load EXR From Path | Load an EXR sequence from any allowed path or drive | | Load EXR Layer | Extract specific named layers (beauty, depth, normal, mask, etc.) from multi-layer EXRs | | EXR Metadata Reader | Inspect EXR header attributes, dimensions, channels, and compression | | ACES Color Transform | Transform between ACES, camera, sRGB, and utility color spaces | | ACES Tone Map | Tone map HDR float tensors with AgX, Filmic, DaVinci, ACES fitted, or Reinhard curves | | Save EXR (Multi-Layer) | Save float EXRs with optional multi-layer passes (depth, normal, mask, diffuse, etc.) | | Nodex HDR Viewer 🎨 | GPU-accelerated (WebGL) 32-bit float viewer with Exposure, Gamma, False Color, and sRGB toggles | | Synthetic HDR Expansion 🚀 | Reconstructs a scene-linear HDR tensor from a standard display-referred (SDR) AI generation | | Exposure Bracket Merge 📸 | Merges a batch of SDR images at varying EV values into a single 32-bit HDR tensor | | HDR Exposure Adjust 💡 | Mathematically adjusts exposure by multiplying tensor RGB values by 2.0 ^ EV |

Nodes appear under:

image/ACES + EXR

Installation

Clone this repository into your ComfyUI custom_nodes folder:

cd D:\Ai\ComfyUI_windows_portable\ComfyUI\custom_nodes
git clone https://github.com/azhagurajpandians/ComfyUI-ACES-EXR-Toolkit.git

Install the optional OpenColorIO dependency into the Python environment used by ComfyUI:

D:\Ai\ComfyUI_windows_portable\python_embeded\python.exe -m pip install -r D:\Ai\ComfyUI_windows_portable\ComfyUI\custom_nodes\ComfyUI-ACES-EXR-Toolkit\requirements.txt

Restart ComfyUI after installation.

Dependencies

Required runtime packages are normally already included with ComfyUI:

• numpy
• torch
• opencv-python or opencv-python-headless

Recommended for ACES Studio 1.3:

• opencolorio (The pip package is named opencolorio; the Python module it provides is PyOpenColorIO.)

Recommended for 16-bit Float and Compression export:

• openexr

ACES Studio 1.3

The default OCIO config is:

ocio://studio-config-v1.0.0_aces-v1.3_ocio-v2.1

That is the OpenColorIO built-in URI for:

studio-config-v1.0.0_aces-v1.3_ocio-v2.1.ocio

Use ACES Color Transform with:

• engine: ACES Studio 1.3 OCIO
• ocio_config: ocio://studio-config-v1.0.0_aces-v1.3_ocio-v2.1
• source: the source color space, for example ACEScg
• target: the target color space, for example sRGB or Utility - Linear - sRGB

You can also point ocio_config to a local .ocio file, or set the OCIO environment variable.

Loading EXR Files

For most EXR work, use Load EXR From Path and paste the absolute file path:

D:\shots\render\beauty.exr

For ComfyUI input-folder workflows, copy EXRs into:

ComfyUI\input

Then restart or refresh ComfyUI and use Load EXR.

Alpha Preview

ComfyUI Preview Image does not display the separate mask output as transparency. For RGBA EXRs, choose an alpha mode that composites RGB for preview:

• composite checker
• composite black
• composite gray
• composite white

The alpha is still exposed separately as the MASK output.

Common Workflows

Preview an ACEScg EXR

Load EXR From Path -> ACES Color Transform -> Preview Image

Recommended transform:

• source: ACEScg
• target: sRGB
• clamp_output: true

If the image is still too bright, insert ACES Tone Map before Preview Image.

Convert Linear sRGB EXR to Display sRGB

Load EXR From Path -> ACES Color Transform -> Preview Image

Recommended transform:

• source: Linear sRGB
• target: sRGB
• clamp_output: true

This will automatically reverse the color space before writing the final .exr file.

The output is written to your selected output directory or ComfyUI's output folder as a 16-bit or 32-bit float EXR.

Nodex HDR Workflow (Synthetic HDR)

If you are generating standard [0,1] AI images (e.g., FLUX or SDXL) and want true High Dynamic Range lighting for post-processing or 3D environment maps:

AI Generator -> Synthetic HDR Expansion 🚀 -> Nodex HDR Viewer 🎨 -> Save EXR

1. Route your SDR image into Synthetic HDR Expansion 🚀 to mathematically reconstruct lost highlights without multi-prompt ghosting.
2. Plug the output into the Nodex HDR Viewer 🎨 to visually inspect the true dynamic range. Try dropping the EV slider or enabling False Color to see the reconstructed highlight data roll off naturally instead of clamping to flat gray!
3. Save the result as a 32-bit .exr using Save EXR.

Verified Round-trip Workflow

For professional VFX work, you often need to go ACES -> sRGB -> ACES. This toolkit provides a dedicated reverse toggle to make this setup easy and accurate.

Key settings for a perfect round-trip:

1. Node 2 (Forward): source: ACES2065-1, target: sRGB, clamp_output: false.
2. Node 3 (Backward): source: ACES2065-1, target: sRGB, reverse: true, clamp_output: false.
3. IMPORTANT: Always set clamp_output to false on intermediate nodes to preserve high-dynamic-range data for the reverse transform.

Troubleshooting

EXR does not show in file picker

Use Load EXR From Path. ComfyUI's upload widget is image-centric and can be unreliable for .exr.

Preview is white

Your EXR likely has transparency and white RGB in transparent pixels. Set alpha_mode to composite checker or composite black.

OCIO mode fails

Install OpenColorIO:

python -m pip install opencolorio

For portable ComfyUI, use its embedded Python:

D:\Ai\ComfyUI_windows_portable\python_embeded\python.exe -m pip install opencolorio

Built-in matrix mode limitations

Built-in matrices supports only:

• sRGB
• Linear sRGB
• ACEScg
• ACES2065-1

Use ACES Studio 1.3 OCIO for camera spaces and full ACES config transforms.

License

MIT License. See LICENSE.