Radiance Viewer

VFX Industry-Standard Image Viewer for ComfyUI

Professional Grade GPU Accelerated Interactive

Overview

The Radiance Pro Viewer brings professional image analysis tools from industry applications like Autodesk Flame, Foundry Nuke, and DaVinci Resolve directly into ComfyUI.

Interactive Navigation

Smooth zoom and pan with mouse wheel and drag gestures.

EXR Export

Save images as 32-bit linear .EXR files for professional compositing.

Professional Scopes

Real-time Histogram, Waveform, and Vectorscope analysis.

Z-Depth Visualizer

View depth maps with correct scaling and normalized visualization.

Exposure Controls

Adjust display EV and gamma for evaluating HDR content.

False Color & Zebra

ARRI-style exposure visualization and clipping detection.

↔ A/B Comparison

Wipe and difference modes for comparing versions.

Fullscreen Mode

Expand viewer to full screen for detailed inspection.

Getting Started

Adding the Node

Search for Radiance Viewer in the ComfyUI node menu, or navigate to FXTD STUDIO → Radiance → Viewer.

First Steps

Scroll Zoom in/out towards cursor
Shift + Drag Pan around the image
Press F Fit image to view
Press 1 100% zoom (1:1 pixels)
Click Sample color values

Interface Layout

Radiance Viewer Interface

Click image to view in full quality

Keyboard Shortcuts

F Fit to View
1 100% Zoom
R Red Channel
G Green Channel
B Blue Channel
L Luminance
C Color (RGB)
H Histogram
W Waveform
V Vectorscope
E False Color
Z Zebra Pattern
A A/B Compare
D Annotate
? Help Overlay
F11 Fullscreen
T Save Snapshot / Download EXR

Professional Scopes

Histogram (H)

Shows the distribution of pixel values across the tonal range. Watch for:

  • Clipping at edges = lost detail in shadows/highlights
  • Gaps in histogram = posterization
  • Bunching = low contrast

Waveform (W)

Displays luminance distribution across the horizontal axis of the image. Vertical position indicates brightness level (0-100%).

Pro Tip

If pixels touch the top of the waveform, highlights are clipping. If they touch the bottom, shadows are crushed.

Vectorscope (V)

Shows color hue (angle) and saturation (distance from center). Useful for checking skin tones and color balance.

False Color Analysis (E)

ARRI-style exposure visualization shows luminance levels as distinct colors:

Purple — <1% Crushed blacks
Blue — 1-8% Underexposed
Cyan — 8-16% Dark shadows
Grey — ~18% Middle grey
Green — 18-35% Optimal
Yellow — 35-55% Bright
Orange — 55-75% Hot
Red — 75-95% Very hot
Magenta — >95% Clipped

Usage

Target skin tones in the green/yellow zone. Avoid magenta (clipped) unless intentional for creative effect.

↔ A/B Comparison

Wipe Mode

Press A to enable split-screen comparison. Drag the divider to compare two images side-by-side.

Difference Mode

Press A again for difference view (5x amplified). Bright areas indicate differences, black indicates identical pixels.

Mode Description
Wipe Draggable split-screen comparison
Difference Highlights pixel differences (5x amplified)

Industry Comparison

Feature Radiance Pro Flame Nuke
Zoom/Pan ◎ ◎ ◎
Exposure Control ◎ ◎ ◎
Histogram ◎ ◎ ◎
Waveform ◎ ◎ ◎
Vectorscope ◎ ◎ ◎
False Color ◎ ◎ ◎
Zebra Pattern ◎ ◎ Plugin
A/B Compare ◎ ◎ ◎
Color Picker ◎ ◎ ◎

HDR Workflow & Display Limitations

Understanding 8-bit Canvas Display

The Radiance Viewer uses the browser's HTML Canvas API for rendering, which is limited to 8-bit color per channel (0-255 values). However, the viewer still supports HDR workflows:

◎ What Works

Internal HDR Processing: The Python backend preserves 16-bit/float data internally. Use exposure controls (EV slider -5 to +5) to inspect different luminance zones of your HDR image.

EXR Export: Use the Save EXR Sequence node for final output with full 32-bit float dynamic range preserved.

Display Limitation

8-bit Canvas Output: The viewer displays 8-bit output in your browser. True HDR monitor display requires 10-bit+ panels and OS-level HDR support, which standard browsers don't expose via Canvas API. The viewer is designed for preview and analysis, not final HDR display.

Recommended HDR Workflow

Step Tool Purpose
1. Generate ComfyUI + Radiance Nodes Create 32-bit float images in linear/LogC4/ACEScg
2. Preview Radiance Viewer Quick preview with EV adjustment to inspect highlights/shadows
3. Export Save EXR Sequence Export full 32-bit float OpenEXR for grading
4. Grade DaVinci Resolve / Nuke Professional color grading with true HDR display support

Pro Tip: Using Exposure Controls

When viewing HDR content, use the EV slider to "develop" different exposure zones:

  • EV -2 to -5: Inspect highlight detail (clouds, specular)
  • EV 0: Normal exposure
  • EV +2 to +5: Inspect shadow detail

This lets you verify that detail exists across the full dynamic range, even though only 8-bit is displayed at once.

Troubleshooting

Viewer not appearing?

  • Restart ComfyUI to load the JavaScript extension
  • Check browser console for errors (F12)
  • Verify js/radiance_viewer.js exists

Scopes not updating?

  • Scopes update when the image changes
  • Toggle scope off/on to force refresh

Performance issues?

  • Reduce preview image size
  • Disable vectorscope (most intensive)
  • Close other scope panels