Diffusion
Softens and spreads bright information into neighbouring image areas.
Resolve FX · ColorTone Diffuser · Resolve 20.1+
ColorTone Diffuser
A light-based diffusion look built around a virtual diffusion filter, coloured Tone Lights, tonal protection, centre-weighted falloff and integrated image compensation.
Diffusion
spatial light scatter
Tone Lights
RGB bias + intensity
LUT mode
3D LUT Compatible
What the effect is modelling
A diffusion filter lit from its perimeter — not a generic soft-focus preset
Blackmagic describes ColorTone Diffuser as a virtual diffusion filter surrounded by a rectangle of user-controlled coloured lights. Their light scatters from the diffusion elements in the glass. That model explains why the plug-in combines spatial diffusion, RGB Tone Lights, a centre-weighted falloff and compensation controls in one effect.
Tone Lights
Adds a content-dependent coloured-light bias, especially visible in darker regions.
Falloff
Weights the effect toward the centre to mimic the physical light distribution around the filter.
Compensation
Exposure, Contrast and Saturation let you normalise the low-contrast result without an extra node when desired.
Every control group
The panel makes more sense when you separate signal, diffusion, tone lights and compensation
Starting point and LUT mode
Presets · 3D LUT Compatible
Presets provide ready-made starting points, while Clean Slate leaves the effect neutral for building a look manually. 3D LUT Compatible puts the plug-in into a mode where Resolve disables controls that cannot be represented in a 3D LUT. That distinction matters: a LUT can remap input RGB values, but it cannot encode spatial diffusion/blur or a position-dependent falloff mask.
- Clean Slate — no change, a base for Custom
- Subtle / Low Contrast / Strong Start / Teal Soft and others are starting looks, not separate algorithms
- In LUT mode, judge only the controls that remain available
Colour Space Overrides
Input Color Space · Input Gamma
By default, Use timeline takes the colour space and gamma from the project's Colour Management settings. If the node receives a signal after a CST, DCTL or another manual transform, the plug-in input may no longer match the timeline state — in that case set Input Colour Space and Input Gamma explicitly. These fields describe the signal; they are not look controls.
- Colour Space = primaries/gamut context
- Gamma = transfer/encoding context
- Use timeline is safe only when the real node input matches the timeline state
Diffusion
Resolution · Diffusion · Amount · Radius
Resolution simulates the slight loss of resolution as light passes through the filter. The Diffusion switch enables spatial spreading of bright areas into neighbouring parts of the frame; Amount controls strength and Radius controls the size of the spreading region. This is not simply a full-frame Gaussian Blur: the goal is to add the character of optical light scatter around bright information.
- Resolution — overall softening/resolution-loss component
- Amount — diffusion strength
- Radius — spatial diffusion radius
Tonal-edge protection
Shadow Soft Clip · Highlight Soft Clip
Shadow Clip protects image values below its Threshold from the ColorTone Diffuser, while Highlight Clip protects values above its own Threshold. Softness controls how gently the effect transitions into bypass. These are not ordinary lift/gain controls; they define the tonal range in which the diffuser is allowed to act.
- Shadow: below threshold the signal bypasses the effect
- Highlight: above threshold the signal bypasses the effect
- Softness keeps the transition from becoming visible
Tone-light colour
Tone Lights · Intensity · Bias RGB
Tone Lights model coloured light sources around the physical diffusion filter. Intensity sets the overall level, while Bias Red/Green/Blue controls the relative contribution of each channel. Blackmagic notes that these bias controls are content-dependent and are usually more visible in shadows, so identical values can look very different on dark and bright material.
- Intensity — overall Tone Light level
- Bias RGB — relative colour balance of the light
- The bias effect reads more strongly in darker regions
Look shaping and normalisation
Tone Light Falloff · Image Adjustments · Global Blend
The Falloff Mask mimics a stronger effect in the centre and weaker edges: Size sets the centre region, Softness shapes the transition, and Amount controls mask influence. Preview Falloff Mask displays the distribution in the Viewer. Image Adjustments provide built-in Exposure, Contrast and Saturation; Advanced Clipping adds a second soft-clip stage at the end of the plug-in. Global Blend finally mixes the complete result with the original.
- Preview Falloff Mask: dark = less effect, white = more
- Advanced Clipping operates after Image Adjustments
- Blend — final wet/dry for the complete plug-in chain
3D LUT Compatible
A LUT can preserve colour mapping — not spatial optics
This switch is not a quality mode. It is a compatibility boundary: Resolve disables parts of the effect that cannot be represented in a 3D LUT. That makes the remaining look exportable to LUT-based devices or stages, while full spatial diffusion/falloff stays a Resolve processing task.
Practical rule: If the final product is a LUT, enable 3D LUT Compatible before designing the look. If the final product is the Resolve render, leave it off unless you specifically need LUT parity.
Production workflow
Six steps from a known signal to a controlled diffusion look
01
Lock the signal state
Confirm what colour space/gamma actually enters the node. Leave Use timeline only when that description is true at this exact point.
02
Start from Clean Slate or a preset
Use presets for direction, then inspect the actual controls. Clean Slate is the cleanest base when you want to understand exactly what each stage contributes.
03
Build diffusion before colour bias
Tune Resolution and, if needed, Diffusion Amount/Radius at 100% viewing size. Avoid compensating a wrong radius with more amount.
04
Shape Tone Lights and falloff
Set Intensity and RGB bias, then decide whether the centre-weighted falloff belongs in the look. Preview the mask instead of guessing its footprint.
05
Protect the tonal ends
Use the pre-effect Shadow/Highlight Soft Clip to keep selected dark/bright regions outside the diffuser. Use Advanced Clipping only when the post-adjustment output also needs protection.
06
Normalise, compare and trim
Use Exposure/Contrast/Saturation to compensate the low-contrast result, then compare with bypass at matched perceived brightness. Finish with Global Blend if the complete look is too strong.
Common failures
Most problems come from a wrong signal description or excessive diffusion
01
Use timeline gives a strange result
Cause: The node input has already been transformed, so timeline colour space/gamma no longer describes the actual signal.
Fix: Set Input Colour Space and Input Gamma to the real node-input state, or move the effect to a stage where Use timeline is correct.
02
The image turns milky and texture disappears
Cause: Too much Resolution softening or an oversized Diffusion Amount/Radius combination.
Fix: Back off Radius first, then Amount. Judge at 100% and compare skin, hair, fine texture and specular edges.
03
Tone Lights look like a flat colour wash
Cause: Intensity is too high, RGB bias is too extreme, or the falloff mask is disabled/too broad for the intended optical feel.
Fix: Reduce Intensity, rebalance the channel bias and preview the Falloff Mask so the spatial distribution is deliberate.
04
The LUT does not match the full plug-in look
Cause: Spatial diffusion/falloff behaviour cannot be encoded in a pointwise 3D LUT.
Fix: Design the LUT with 3D LUT Compatible enabled and treat the remaining spatial components as Resolve-only processing.
Creative optical look, not a technical transform
ColorTone Diffuser: the signal-level model
The most useful mental model for ColorTone Diffuser is a digital diffusion filter with coloured lights around its perimeter. The plug-in does more than reduce sharpness: it combines light scatter, RGB Tone Lights, tonal bypass, centre-weighted falloff and Exposure/Contrast/Saturation compensation in one creative-look operation.
Blackmagic describes the physical metaphor explicitly: the colour and intensity of the virtual lights alter the light scattered by diffusion elements in the glass. Resolution simulates slight resolution loss, Diffusion spreads bright areas, Shadow/Highlight Soft Clip excludes the tonal extremes, Tone Light Falloff provides spatial weighting, and Image Adjustments compensate the resulting low-contrast look.
3D LUT Compatible is not a quality switch. It disables controls that cannot be represented in a 3D LUT. A LUT created from the compatible subset therefore cannot be expected to reproduce the full spatial diffusion/falloff look. Separately, Use timeline is correct only when the timeline Colour Management settings actually describe the signal state entering this node.
Use it when
- a soft low-contrast optical look with controllable coloured light scatter
- building a distinctive look from Clean Slate or a preset in one dedicated FX node
- designing the LUT-compatible part of a look when spatial components can remain separate inside Resolve
Choose another tool when
- you only need neutral blur/defocus without the tone-light model — use the appropriate Blur/Focus FX
- you need a technical conversion between colour spaces/gammas — use CST/RCM/ACES, not ColorTone Diffuser
- you need a measured physical replica of a specific real-world filter rather than a creative interpretation
Control → signal meaning → verification
| Layer | What it means | How to verify |
|---|---|---|
| Presets + Clean Slate | Ready-made starting looks; Blackmagic documents Clean Slate as making no changes, providing a neutral base for Custom. | After choosing a preset, inspect the actual controls rather than relying on its name. |
| 3D LUT Compatible | Restricts the plug-in to operations that can be represented in a 3D LUT; incompatible controls are disabled. | Enable it before look development when the deliverable must be a LUT; do not compare the exported LUT with full spatial mode as if they were the same system. |
| Input Colour Space + Gamma | Describes the colour state received by the effect. Use timeline takes the values from the project's Colour Management settings. | After CST/DCTL/manual transforms, verify that the real node input still matches the timeline description. |
| Resolution + Diffusion Amount/Radius | Resolution simulates slight resolution loss, while Diffusion spreads bright regions; Amount sets strength and Radius sets spatial extent. | Inspect at 100%: skin texture, hair, fine detail, specular edges and halos. |
| Shadow / Highlight Soft Clip | Pre-effect tonal protection: values below the shadow threshold or above the highlight threshold bypass the diffuser with adjustable Softness. | Watch for a seamless transition and do not confuse these controls with ordinary tonal grading. |
| Tone Lights + Bias RGB | Intensity sets the overall level of the virtual lights, while Bias RGB sets their relative colour mix; the documentation notes content dependence and greater visibility in shadows. | Check skin/neutrals and RGB Parade/Vectorscope, especially in darker regions. |
| Tone Light Falloff | A spatial vignette-like mask: stronger in the centre and weaker toward the edges. Size, Softness and Amount define geometry/strength. | Use Preview Falloff Mask: dark = less effect, white = more effect. |
| Image Adjustments + Advanced Clipping + Blend | Exposure/Contrast/Saturation compensate the look inside the plug-in; Advanced Clipping adds a post-adjustment soft-clip stage; Blend is the final wet/dry. | Compare bypass at matched perceived brightness and inspect highlights after compensation. |
Production workflow
- 01Identify the node's real input colour state before deciding whether Use timeline is appropriate.
- 02Choose Clean Slate for controlled construction or a preset as a starting point; for LUT delivery, enable 3D LUT Compatible first.
- 03Tune Resolution and Diffusion Amount/Radius at 100% until the softening preserves the required texture.
- 04Tune Tone Light Intensity/Bias RGB and the Falloff Mask, using Preview rather than guessing the spatial footprint.
- 05Constrain the effect with Shadow/Highlight Soft Clip, then compensate Exposure/Contrast/Saturation; if needed enable post-stage Advanced Clipping and finish by trimming the result with Blend.
Diagnostics: symptom → cause → fix
The look changes dramatically after moving the node
Likely cause: Input Colour Space/Gamma no longer match the new signal state.
Fix: Redescribe the plug-in input or return the node to the stage for which it was tuned.
The image is too milky and detail is lost
Likely cause: Resolution/Diffusion Radius/Amount are too high together.
Fix: Reduce Radius and Amount independently, then re-check texture at 100%.
Tone Light colour varies too much between shots
Likely cause: Bias RGB is content-dependent; the shots differ in shadow level and colour structure.
Fix: Match by visual result/scopes rather than copying numbers; use a shared baseline plus shot trims across a sequence.
The exported LUT looks different from the Resolve node
Likely cause: The full node uses spatial operations that a 3D LUT cannot represent.
Fix: Develop the LUT only in 3D LUT Compatible mode and document the Resolve-only spatial stages separately.
Node placement
In practice, ColorTone Diffuser is easiest to manage on a dedicated creative-look node after the input has reached a known working state, but before any stage that must see the unmodified signal. This is not a hard rule: the plug-in has Input Colour Space/Gamma overrides precisely because it can operate in different states. The key is to describe its input unambiguously and keep the ordering consistent across shots.
Scopes / validation
A 100% Viewer is more important than scopes for spatial diffusion, texture and halos. Waveform helps validate contrast/exposure and soft-clip boundaries; RGB Parade/Vectorscope help with Tone Light bias and neutrals. Preview Falloff Mask is the primary tool for checking spatial weighting.
Managed-pipeline warning
In RCM, Use timeline reads the project Colour Management state, but it cannot account for every manual CST/DCTL rearrangement you make inside the node tree. If gamut/gamma has already been changed before ColorTone Diffuser, the overrides must describe the actual signal. Do not confuse these overrides with an output transform: they tell the plug-in how to interpret its input rather than replacing the whole project colour-management pipeline.
Do not confuse the roles
ColorTone Diffuser versus the neighbouring Color FX
Color Space Transform
explicit conversion between colour-space/gamma descriptions, including tone/gamut mapping
Open guide
ACES Transform
node-level input/output through the standardised ACES transform set
Open guide
Chromatic Adaptation
conversion between white points / illuminants through a CAT model
Open guide
Color Compressor
compressing hue/saturation/luminance variation around a selected Target Color
Open guide
Color Stabilizer
temporal matching of unwanted brightness/white-balance drift around a chosen reference and analysis region
Open guide
Contrast Pop
selective increase or reduction of local contrast at a chosen structure scale and within a controlled tonal range
Open guide
DCTL
programmable host for custom transform code whose maths, UI and signal contract are defined by the selected DCTL/DCTLE
Open guide
Dehaze
depth-weighted reduction of smog/airlight/haze through a simulated depth matte and coupled colour/contrast correction
Open guide
Despill
suppression of reflected red/green/blue screen spill after the subject has already been isolated by key/matte/roto
Open guide
False Color
spatial display of exposure zones through camera-matched or creative false-colour mapping and a legend
Open guide
Gamut Limiter
final hard-clipping of chromaticities to a specified delivery/QC gamut boundary
Open guide
Gamut Mapping
tone/gamut remapping through luminance roll-off, saturation compression/clip and OOTF without a separate input/output colour-space conversion
Open guide
Invert Color
simple independent inversion of Red/Green/Blue/Alpha channels for creative and technical channel/key operations
Open guide
NVIDIA RTX Video HDR
AI-assisted SDR→HDR mapping with an explicit input/output signal contract, Middle Gray, target peak luminance and creative shaping
Open guide
Camera Shake
procedural Pan/Tilt/Rotation/Zoom motion with waveform, randomness, pauses and blanking handling
Open guide
Film Damage
procedural texture/look effect combining blur/colour drift, vignette, changing dirt and up to five scratches with motion/flicker
Open guide
Film Grain
procedural film-style texture with gauge presets, grain geometry, composite modes, tonal/RGB weighting and final mix
Open guide
Film Look Creator
integrated scene-referred film-emulation environment combining a baked-in Blackmagic film response, colour shaping, halation/bloom/grain/flicker/gate weave and a LUT-compatible subset
Open guide
Flicker Addition
dedicated temporal exposure modulation with tonal flicker modes, RGB selection, smoothness, randomness, pauses and a deterministic seed
Open guide
Halation
film-style highlight scatter using an isolation matte, chromatic dye-layer reflections, secondary glow and optional grain
Open guide
Split Tone
creative shadow/highlight colour separation through Natural/Strong/Custom modes, Pivot, Hue Angle, neutral protection and colour-space overrides
Open guide
Vignette
edge framing and visual-attention control through Basic/Advanced geometry, position, colour and compositing
Open guide
Color Generator
solid-colour generation for Layer Mixer, masks, fills and simple colour washes
Open guide
Colour Space
Primaries, white point and the meaning of RGB coordinates are already covered here.
Related chapter
Gamma / Transfer Functions
Why Input Gamma describes encoding rather than acting as a creative contrast slider.
Related chapter
Colour Management
Where timeline state comes from and how to avoid a wrong Use timeline after manual transforms.
Related chapter
Node pipeline
How to separate technical transforms from creative look nodes and shot trims.
Related chapter
Primary references used for this technical layer
Blackmagic Design · DaVinci Resolve 20.1 New Features Guide
Primary ColorTone Diffuser reference: physical light/diffusion model, Presets, 3D LUT Compatible, Colour Space Overrides, Diffusion, Soft Clip, Tone Lights, Falloff and Image Adjustments.Blackmagic Design · DaVinci Resolve Color
Current context for the Color page, node-based grading, colour management and scopes.Blackmagic Design · DaVinci Resolve Support
Current Resolve builds, manuals and release documentation.
Primary ColorTone Diffuser reference: physical light/diffusion model, Presets, 3D LUT Compatible, Colour Space Overrides, Diffusion, Soft Clip, Tone Lights, Falloff and Image Adjustments.Blackmagic Design · DaVinci Resolve Color
Current context for the Color page, node-based grading, colour management and scopes.Blackmagic Design · DaVinci Resolve Support
Current Resolve builds, manuals and release documentation.
Panel names are cross-checked against the Resolve 21 screenshots already shown on each page. Where Blackmagic does not publish proprietary implementation math, the article describes documented signal semantics and observable behaviour rather than inventing an algorithm.
FAQ
Practical ColorTone Diffuser questions
Is ColorTone Diffuser just another Glow?
No. Its documented model combines diffusion-filter softening, coloured Tone Lights, tonal protection, spatial falloff and integrated image adjustments. Glow is centred on spreading luminance around bright regions; the intent and control architecture are different.
What does Clean Slate do?
Blackmagic describes Clean Slate as the default preset that makes no changes, so it is the correct baseline for building a custom look from zero.
Why are Tone Light RGB biases stronger in shadows?
Blackmagic explicitly notes that the bias controls are content-dependent and more visible in shadows. Do not expect the same numeric bias to produce the same apparent colour shift on every shot.
When should I enable 3D LUT Compatible?
Enable it when the end product must be representable as a 3D LUT for a camera, monitor or another LUT-based stage. Resolve will disable controls that cannot be passed through that format.
Should the effect be before or after the output transform?
There is no universal answer. The critical rule is that Input Colour Space/Gamma must describe the signal reaching the plug-in. For a scene-referred look workflow, placing it in a known working state is usually easier to manage than applying it blindly after a display transform.
Why does Image Adjustments include clipping options again?
The original Shadow/Highlight Soft Clip protects the signal before the core diffuser. Advanced Clipping is applied at the end of the plug-in, after Image Adjustments, so it can catch values created by the final exposure/contrast/saturation compensation.
Next steps
Keep optical look design separate from signal transforms
Previous FX
Camera Shake
Return to procedural transform motion, waveform shaping, randomness and blanking handling.
Color Management
Review where timeline colour space/gamma come from before relying on Use timeline.
Colour Space
The underlying theory of primaries, white point and RGB coordinates already lives in Color Science.
Next FX
Film Damage
Continue with blur/colour drift, vignetting, procedural dirt and five scratch layers.
Film Damage