Blur

Blur looks simple, but a production result is not controlled by Blur Size alone. You make separate decisions about the filter kernel, participating channels, linked or independent axes, frame/domain edge behavior and the final dry/wet mix.

The main signal path stays ordinary 2D image data: Input → Blur → Output. The blue Effect Mask is not a second picture, a depth map or a radius control. It only limits where the already computed operation contributes to the result.

The bundled Inspector captures confirm Filter, R/G/B/A buttons, Lock X/Y, Blur Size, Clipping Mode and Blend. The second capture opens the Filter menu and confirms Box, Bartlett, Multi-box, Gaussian and Fast Gaussian. Those captures are the current UI evidence for this page.

Filter changes how neighboring pixels are distributed. Compare kernels with the same frame, Blur Size, channels and clipping state; otherwise an A/B changes more than one variable and tells you very little.

Box is a simple hard baseline. Bartlett has a different falloff profile. Multi-box is a distinct fast/smooth option. Gaussian gives the classic soft profile, while Fast Gaussian is an optimized Gaussian-like choice that is often practical while building the comp. Exact performance and pixel response should still be checked on the target Resolve/GPU.

Blackmagic's historical Blur Tool Reference notes that every practical Gaussian is an approximation and that extreme float-depth cases can reveal ringing; it suggests Multi-box as a possible alternative. Treat that as a diagnostic clue rather than a claim that current Resolve 21 will always show the artifact.

The R, G, B and A buttons decide which image components Blur actually processes. RGB blur changes color detail; Alpha blur changes the geometry of a transparency edge. On titles, PNGs, keyed subjects and roto elements those are different operations and should be inspected separately.

With Alpha disabled, RGB can become softer while the matte stays unchanged. With Alpha enabled, the transparent boundary can spread or soften along with color. Inspect RGB and Alpha viewers independently, especially on premultiplied graphics.

Lock X/Y links blur geometry on both axes. In the captured state it is enabled and the Inspector shows one Blur Size. Unlocking allows directional axis control; exact labels in the expanded target-build state remain a live-verification item because the current capture only proves the linked state.

Blur Size sets the scale of the filter. Do not copy a number as a universal preset between 1080p, UHD and differently sized graphics: visible softness depends on resolution, source domain and the element being processed.

Clipping Mode is a separate edge policy. The current capture confirms None, Domain and Frame. Test it with a bright or alpha-edged object close to the image boundary; a centered object rarely exposes the difference clearly.

Do not confuse Clipping Mode with Crop, a mask shape or final timeline framing. It concerns Blur behavior at the source domain/frame boundary rather than editorial framing.

Blend is the node's final dry/wet control. At 1.0 the full processed result is used; reducing Blend restores more of the original Input. It is useful for subtle softening, but it does not replace a separate Merge when branches need independent transforms or compositing modes.

For privacy blur, the correct topology is MediaIn → Blur → MediaOut with Polygon/Rectangle → Blur.Effect Mask. The mask defines where, Filter and Blur Size define how, and Input defines what is processed.

For a shadow or halo-preparation pass, keep Blur on a separate branch before Merge. The sharp core then stays independent while the soft branch can be offset, colored, mixed or disabled without touching the original.

If the only problem is a hard mask edge, try Soft Edge on Polygon/Rectangle/B-Spline first. Image Blur filters pixels; mask feather changes mask coverage. They solve different problems.

Blur is also useful as a prefilter for procedural maps: Fast Noise, Blobs or another texture → Blur → threshold, displacement or glow. Here the goal is to remove high-frequency structure before a later stage amplifies it.

Placement relative to Merge is critical. Blur before Merge changes only that branch; Blur after Merge filters the already assembled composite. Many accidentally soft titles are simply a node-order problem.

On transparent graphics, inspect premultiplied edges. Strong RGB/Alpha blur can reveal color fringe that is invisible in the Alpha Viewer. Separate matte problems from RGB problems before changing the creative settings.

The Settings tab is visible in the Inspector but its hidden controls are not captured here. This article therefore does not invent target-build Settings labels from another version; general Fusion settings remain separate from Blur-specific Controls.

Final QC should not be limited to a still frame. With tracked masks, animated transforms or moving sources, watch playback for hard mask boundaries, lag, frame-edge halos and texture shimmer.

This page is anchored to two bundled Resolve Inspector captures plus Blackmagic's historical Blur reference. Exact pixel response, filter performance and unlocked X/Y labels should be live-verified on the target Resolve 21/21.1 build before publishing production presets.