ColorToneDiffuser

**What this effect is.** ColorToneDiffuser models a diffusion filter illuminated by controllable colored lights arranged around it. It combines spatial scatter from bright detail with colored tonal light; it is not simply a per-channel blur.

**Resolve FX, not a generator.** It processes an existing 2D picture. The project screenshots document the Resolve 21 Inspector, not its physical Flow sockets; this article labels its image-in/image-out graph as editorial until verified in Resolve.

**Separate signal, optics, light and finish.** First establish the true input color state. Next come resolution softening and spatial diffusion, tonal bypass protection, RGB Tone Lights with falloff, then independent Exposure/Contrast/Saturation compensation.

**Presets are starting states.** The captured dropdown lists Clean Slate, Subtle, Low Contrast, Strong Start, Teal Soft, Teal High Contrast, Comfy Couch, Diner Crunch, Warm Diner and Custom. Inspect the resulting controls rather than treating those names as distinct processing engines.

**Clean Slate is neutral.** Blackmagic documents Clean Slate as a no-change starting point. Select it before changing parameters so that the contribution of Diffusion, Tone Lights and final adjustments can be examined independently.

**3D LUT is a capability boundary.** 3D LUT Compatible disables controls that cannot be encoded in a LUT. A lookup table describes RGB remapping, not neighborhood-dependent diffusion or position-based falloff; never promise that the exported LUT recreates full spatial optics.

**Input Color Space and Input Gamma are separate.** The former describes primaries/gamut, the latter the signal transfer curve. Use timeline inherits project color-management settings and is reliable only if they describe the actual input at this node.

**Recheck the signal after a CST.** An upstream ColorSpaceTransform, DCTL or LUT may have changed the frame before it reaches this effect. The timeline defaults can then be wrong; declare the incoming gamut/gamma deliberately and avoid redundant transforms.

**Resolution represents optical softening.** Blackmagic describes it as simulated detail loss through the filter, not the Diffusion Radius. Check skin texture, fine hair and small lettering at 100% viewing rather than judging from a reduced preview.

**Diffusion is not generic Blur.** The Diffusion toggle spreads bright image information into neighboring pixels. Amount changes strength and Radius changes spatial reach; an oversized radius can swamp specular edges and local contrast.

**Set Radius before pushing Amount.** On a shot with visible highlights, choose the spatial spread first, then intensity. A wide weak halo is not interchangeable with a tight strong one, even if a downscaled viewer makes them appear similar.

**Shadow Soft Clip is pre-effect protection.** Shadow Clip makes values below its Threshold bypass the diffuser, with Softness smoothing that transition. It protects blacks and shadows from the optical stage; it is not a Lift control or a separate image mask.

**Highlight Soft Clip is also pre-effect.** Highlight Clip bypasses the diffuser above its Threshold and Softness controls the rolloff. It may protect specular detail, but protecting original highlights is different from merely reducing their bloom.

**Tone Lights are not a conventional shadow grade.** Colored lights around the simulated glass produce additional scatter. Intensity controls level and Bias Red/Green/Blue their mix; Blackmagic notes strong content dependence and more visible results in dark areas.

**RGB bias is not guaranteed to be a linear add.** Do not interpret the displayed values as fixed pixel-channel offsets. Evaluate with a vectorscope, neutral objects and skin—especially when a preset modifies several controls at once.

**Falloff is an internal mask.** Apply Falloff Mask models stronger light near the center and less at the edges. Size sets the center region, Softness the slope and Amount the strength; this is not a separate Flow mask input or a general Power Window.

**Preview Falloff Mask is diagnostic.** White regions indicate more effect and dark regions less. Disable Preview before assessing final color or comparing effect on/off, because the diagnostic mask is not the finished grade.

**Image Adjustments are the finishing stage.** Enable Adjustments unlocks Exposure, Contrast and Saturation for compensating the low-contrast optical result. They are not spatial-diffusion settings and should be adjusted after the optical look is established.

**Advanced Clipping is downstream.** Show Advanced Clipping Options reveals a second shadow/highlight soft-clip stage applied after Image Adjustments. Its position matters: this second pair protects the compensated output rather than the initial optical stage.

**Practice and evidence boundary.** The lessons separate diffusion, LUT-safe color operations, tone-light look and localized compositing through the verified Merge/Rectangle route. The FX tool’s physical socket labels, alpha response and GPU-rendered results remain pending native Resolve tests.