Resolve FX · Blur · 01

Box Blur DaVinci Resolve

Box Blur is a flexible baseline Resolve FX blur with independent horizontal and vertical control, per-channel adjustment, iterations for smoothness, edge handling and a final global blend.

The page uses the real DaVinci Resolve 21 panel so every control below corresponds to the interface you actually see in Resolve.

StrengthSplit H/VIterationsBorder TypeGlobal Blend

Read the controls Resolve FX catalog

Variable strength

Start with overall Strength, then split H/V only when the shot actually needs separate directions.

Per-axis control

Horizontal and Vertical blocks can shape the blur independently instead of forcing a symmetrical result.

Iterations change smoothness

Use iterations to move from a more obvious box-like blur toward a softer result.

Blend at the end

Shape the effect first, then use Global Blend to decide how much of it should remain in the final image.

Controls

Read the panel from top to bottom

Box Blur looks simple, but it becomes much more flexible once H/V splitting, channel controls, iterations and border handling are used deliberately.

Strength and Horizontal Channel Adjustment

Strength controls the overall intensity. When Split Horizontal and Vertical is enabled, the horizontal and vertical components can be adjusted separately. Red, Green, Blue and Alpha then let you control horizontal blur channel by channel.

Strength sets the overall blur amount

Split enables independent H/V controls

RGB + Alpha provide channel-level control

Vertical Channel Adjustment

The vertical block follows the same logic but controls top-to-bottom blur. It is useful when the effect should not be symmetrical or when a particular channel needs a different vertical response.

Blur can be stretched along one axis

Each channel can be adjusted independently

Works together with Split H/V

Iterations, Border Type and Blur Alpha

Number of Iterations controls how smooth Box Blur becomes: fewer iterations retain a more obvious box-like structure, while more iterations soften the result. Border Type defines how image edges are handled, and Blur Alpha includes the alpha channel in the blur.

Iterations changes the smoothness of the result

Border Type affects frame edges

Blur Alpha matters when transparency is involved

Global Blend

Global Blend is a fast way to reduce an already configured Box Blur without rebuilding the other controls. A practical approach is to shape the blur first, then pull it back with the final Blend control.

1.000 gives the full FX result

Lower values reveal more of the original image

Useful for final effect dosing

Border Type

What happens at the edges of the frame

Blur needs pixel information beyond the frame edge. Border Type defines where that information comes from, so the choice becomes visible whenever a strong blur reaches the border.

Black

Outside pixels are treated as black. Strong blur near the frame edge can therefore pull darker values into the image.

Replicate

The edge pixels are extended outward. This often keeps borders more stable when you do not want a dark edge to appear.

Reflect

The image is mirrored beyond the edge. It can create a smoother continuation when the blur reaches outside the frame.

Wrap-Around

Pixels wrap from the opposite edge of the frame. It is a specialised option and can produce obvious cross-edge interaction.

Practical use

Where Box Blur is actually useful

Local censor or privacy blur

Put Box Blur on a separate node, limit it with a Power Window or mask and track the region if it moves.

Soft background separation

A restrained blur behind the subject can simplify a busy background, but it should support the shot rather than look like an obvious filter.

Directional-looking softness

Split Horizontal and Vertical lets you create a more stretched result instead of a fully symmetrical blur.

Channel-specific experiments

Separate Red, Green and Blue controls allow stylised chromatic softness when you deliberately blur channels by different amounts.

Box Blur vs Gaussian Blur

Choose by behaviour, not by the word blur

Box Blur

When you want iterations and strong H/V control

Box Blur is useful when you want a simple blur algorithm that can be shaped through iterations, independent axes and channel controls. At lower iteration settings its character can remain visibly more box-like.

Gaussian Blur

When the target is a naturally smooth blur profile

Gaussian Blur is a different blur method and is usually the more direct choice when the visual goal is simply a soft, smooth blur without using Box Blur iterations as part of the look.

Node workflow

Keep the blur on a separate, readable node

Create a dedicated FX node

Keep Box Blur separate from primary balance and creative color decisions.

Limit the area if needed

Use a Power Window, Qualifier or another matte source when the blur should be local.

Shape Strength, axes and edges

Only split H/V or change Border Type when the shot actually benefits from it.

Finish with Global Blend

Pull the final intensity back until the effect supports the image instead of dominating it.

Technical model

Box Blur: how the effect behaves in a real node tree

Box Blur is easier to understand as a spatial filter rather than just another blur slider: its character is shaped by neighbourhood size, repeated passes, independent axes and edge-extension rules.

In practice, low Iterations preserve a more geometric box-like character while repeated passes smooth the profile. Split H/V turns a symmetric blur into an anisotropic one. Resolve does not publish the exact internal kernel or Strength-to-radius mapping, so UI values should not be treated as literal pixel radii.

Judge the result at 100%: fine structure and edge contamination can disappear at Fit-to-view.

Use it when

fast local blur in a dedicated node with a Power Window
different horizontal and vertical blur amounts
stylised per-channel RGB/Alpha blur

Choose another tool when

you need realistic aperture-shaped defocus — prefer Lens Blur
blur must depend on scene depth — use AI CineFocus

What each control changes — and what to inspect

Control / layer	Meaning	Inspection point
Iterations	Changes the character of repeated averaging and the smoothness of the profile.	Compare thin high-contrast edges and small text.
Split H/V	Decouples the axes so you can create horizontal smear without equal vertical softening.	Make sure the stretch serves the shot rather than looking accidental.
RGB / Alpha	Unequal RGB values create coloured edges; Alpha changes the transparency contour.	Check RGB Parade and the edge matte when the effect is technical rather than stylised.
Border Type	Defines how missing samples beyond the frame are supplied.	A strong blur touching the frame edge is the best test for Black/Replicate/Reflect/Wrap.

Production workflow

01Use a dedicated serial node for the FX so it is easy to bypass, mask and compare.
02Set Strength first with linked H/V and equal RGB channels.
03Only then split H/V or channels if the shot genuinely needs it.
04Tune Border Type on the most problematic frame edge, not in the centre.
05Limit the effect with a Window/Qualifier and finish with Global Blend.

Diagnostics: symptom → cause → fix

Dark edge halo

Likely cause: Black border samples are entering the blur.

Fix: Try Replicate or Reflect.

Coloured fringes

Likely cause: RGB channel adjustment values differ.

Fix: Equalise RGB for a neutral blur.

Blur looks coarse or boxy

Likely cause: Too few Iterations for the current strength.

Fix: Increase Iterations or switch to Gaussian Blur.

Performance

Iterations and larger blur extents increase processing cost. Keep the effect only as strong as necessary while working interactively, then judge final settings at delivery resolution.

Animation & keyframes

In Resolve 20+, Resolve FX parameters can be exposed in the Keyframe/Curve Editor. When animating Strength or H/V, smooth the curves — a linear jump in blur often reads as a technical transition rather than an optical change.

Node placement

For a normal grade, place Box Blur after primary exposure/colour corrections but before final sharpening or grain. If the blur must affect a matte or key, node placement follows that tree’s logic rather than a universal rule.

Choose by geometry

When Box Blur is not the right FX

Gaussian Blur

smoothly weighted blur without a directional vector

natural softness, defocus beds and clean-up

Open guide

Directional Blur

linear vector driven by Angle

motion smears and horizontal/diagonal streaks

Open guide

Lens Blur

aperture and bokeh profile

optical defocus character without depth analysis

Open guide

Mosaic Blur

discrete cells and pixelation

detail concealment and graphic stylisation

Open guide

Radial Blur

rotation around a centre

spin, vortex and rotational motion

Open guide

Zoom Blur

rays toward or away from a centre

rush, punch-in/out and depth-like transitions

Open guide

AI CineFocus

depth-aware virtual lens

different defocus across foreground, subject and background

Open guide

Nodes and pipeline

Where to place FX and preserve operation order.

Related chapter

Qualifier · Windows · Tracker

How to localise blur and keep the matte tracked over time.

Related chapter

Sizing

Coordinates, crop/zoom and FX-centre behaviour after transforms.

Related chapter

Scopes

Check RGB contamination, clipping and technical side effects.

Related chapter

Primary references used for this technical layer

DaVinci Resolve 21 · New Features Guide
AI CineFocus and current Resolve 21 behaviour.DaVinci Resolve 20 · New Features Guide
Keyframable Open FX / Resolve FX in the Keyframe and Curve Editor.Blackmagic Design · Color
Official Color page and Resolve FX workflow context.

Control names and panel layout are also cross-checked against the real DaVinci Resolve 21 screenshots shown earlier on this page. Where Blackmagic does not publish implementation math, this guide describes observable behaviour and does not invent a proprietary kernel.

FAQ

Box Blur in DaVinci Resolve: common questions

What does Number of Iterations do in Box Blur?

It controls how smooth the blur becomes. Lower settings keep a more obvious box-like structure, while additional iterations soften the result.

Why split Horizontal and Vertical blur?

It lets you make the blur stronger along one axis than the other, or apply different channel values horizontally and vertically.

What is Blur Alpha for?

It includes the alpha channel in the blur. This matters when the node is working with transparency or a keyed element rather than only a full opaque frame.

Which Border Type should I use?

There is no universal choice. Replicate and Reflect are often useful when you want cleaner-looking frame edges, while Black and Wrap-Around create different edge behaviour that may be appropriate for specific tasks.

Is Box Blur the same as Gaussian Blur?

No. They are different blur methods. Box Blur exposes iterations and can retain a more box-like character at low settings, while Gaussian Blur is generally chosen for a naturally smooth blur profile.

Related Blur FX