RH Hybrid Dye Engine
RH Hybrid Dye Engine is an advanced film emulation and color grading tool that runs two completely distinct image processing pipelines in parallel and intelligently blends them based on scene exposure. By fusing a rigorous spectral film dye simulation with a pristine digital tone curve, it delivers the thick, rich colors of celluloid in the shadows and the clean, unbound highlights of modern digital sensors.
Crucially, it features Multi-Layer Emulsion Modeling and DIR Coupler Interimage Effects, giving you authentic color separation and organic density without ever muddying your highlights or fighting your camera's dynamic range.
Density-Dependent Crossfade Architecture Runs two parallel grading paths: as image density increases (shadows), it is driven by a spectral film dye model; as density decreases (highlights), it smoothly crossfades into a clean, additive digital tone curve to prevent highlight twisting.
Multi-Layer Emulsion & DIR Couplers Simulates fast (large grain) and slow (fine grain) sublayers for customizable contrast roll-off, while modeling chemical Development Inhibitor Releasing (DIR) couplers to organically separate colors without muddying saturations.
Spectral Integration Evaluates light absorption against standard Illuminant D65 lighting and CIE observer matching functions for true physical dye rendering.
Physical Film Artifact Controls True silver retention for authentic bleach-bypass contrast, physical halation emulation that reduces cyan dye in high-contrast boundaries, and adjustable fog levels for lifting D-Min base density.
- 1. Core Concept
- 2. Multi-Layer & Blend Controls
- 3. Color & Physical Characteristics
- 4. Dye Tuning
- 5. Visual Aids
- 6. Node Placement
The engine splits the incoming scene-referred log signal into two parallel paths:
- Path A (Subtractive Spectral Dye Model): Simulates the physical absorption of Cyan, Magenta, Yellow, and Silver dyes exactly how physical film absorbs photons.
- Path B (Additive Digital Tone Curve): Processes the image using a mathematically pristine, additive digital curve that preserves exact RGB ratios and applies a clean highlight roll-off without color twisting.
A Blend Controller seamlessly crossfades between them
Balances the response between the dual sublayers inside the emulsion:
-
Default:
0.3 - Fast Sublayer: Simulates large, highly sensitive grains for soft, smooth highlight roll-offs.
- Slow Sublayer: Simulates fine, low-sensitivity grains for thick, punchy shadow contrast.
- Higher values favor softer highlights; lower values produce denser, crunchier shadows.
Controls the intensity of the Development Inhibitor Releasing (DIR) couplers.
-
Default:
0.5 - As one dye layer builds density during development, it chemically inhibits adjacent layers. This cross-channel subtraction creates the legendary color separation of cinema (e.g., preventing reds from becoming muddy).
Determines the global maximum dominance of the film chemistry path versus the clean digital path.
-
Default:
0.6 -
1.0= 100% subtractive film chemistry;0.0= 100% additive digital curve.
Shapes the steepness and pivot of the crossfade curve between the filmic shadows and digital highlights.
-
Default:
1.0
Push or pull the effective exposure of the signal before it hits the spectral dye layers.
-
Default:
0.0 -
Range:
-3.0 to +3.0 EV
- Contrast: Adjusts the global contrast curve across both pipelines.
- D-Max: Sets the maximum density ceiling for the physical dye absorption model.
Global saturation and dye intensity scale.
-
Default:
1.0
Raises the base density of the film emulsion (D-Min).
-
Default:
0.02 - Lifts deep shadows and reduces overall macro-contrast to simulate vintage or un-blipped film stock.
True physical bleach-bypass emulation.
-
Default:
0.0 - Retains spectrally accurate neutral silver halide density in the emulsion before integration, delivering gritty contrast and organic desaturation.
Simulates light scattering on film backing layers.
-
Default:
0.0 - Physically reduces cyan dye generation in bright high-contrast boundaries, producing a natural red/orange halation glow without artificial blurring.
These sliders allow you to physically tune the spectral absorption multipliers for each individual dye layer before CIE color matching integration.
| Slider | Action |
|---|---|
| ⚪ Cyan Dye Strength | Scales red-light absorption. Increase for deeper teals; decrease for cleaner reds. |
| 🟣 Magenta Dye Strength | Scales green-light absorption. Increase for punchier magentas/reds; decrease for cleaner greens. |
| 🟡 Yellow Dye Strength | Scales blue-light absorption. Increase for richer golds/yellows; decrease for cooler blues. |
Overlays a live graph showing the physical transfer curves directly on your viewer.
- Orange Line: Subtractive Path A (Physical Dye density curve).
- Green Line: Additive Path B (Digital tone curve).
- Gray Line: Linear 1:1 reference.
- Use this diagnostic tool to visually balance your Fast-Slow Ratio, Contrast, and Blend Transition right in the viewer!
Expected pipeline:
- Scene-referred log input (e.g., DaVinci Wide Gamut / Intermediate or Arri LogC4).
Recommended placement:
- Primary Look Anchor: Place near the end of your grading node tree, after primary balance and exposure corrections, but before any display output transform (e.g., Kodak 2383 Print LUT or Rec.709 ODT).
- Because the blending between Film and Digital paths is density-dependent, feeding a properly exposed signal into this node ensures the shadows receive thick film density while highlights remain clean and modern.