Motion blur

Motion blur streaks a moving clip along the way it moved during each frame, as a camera’s shutter would. It takes the hard steps out of a fast zoom, pan or slide.

Where: Clip tab ▸ Picture sub-tab ▸ Transform ▸ Motion Blur
Agent tools: set_videoset_action_end

Add motion blur

Select a clip that moves.
On the Clip tab’s Picture sub-tab, open Transform.
Raise Motion Blur above 0%.

Motion Blur runs from 0 to 100%, with quick picks at 0, 25, 50 and 100. It’s off by default.

The number is the share of one frame the shutter stays open for. 50% is a film camera’s 180° shutter, so it’s a good place to start. At 100% the clip streaks along everything it moved in that frame.

The blur shows when the clip moves:

A zoom or pan in an action.
A motion preset.
The nest it sits in moving.

A clip’s recorded cursor streaks along its own path too, even when the clip stands still. The cursor’s click ripples stay sharp.

The Transform section’s Reset puts Motion Blur back to 0% with the section’s other rows.

Auto Zoom has a Motion blur box of its own. Ticked, it sets 50% on the clips it zooms, unless they already have a blur.

How it is drawn

The blur is the same in the preview, in Save Frame, in every export and in a frame an agent renders. Each frame draws the clip 16 times at its positions across the shutter and averages them. The shutter is centred on the frame.

A clip that doesn’t move in a frame draws exactly as it does with the blur off, so a clip that moves for only part of its length blurs only while it moves.

Ramp the blur in and out

Motion Blur can change inside an action, so a blur can build up and fall away.

Select the action.
Set Motion Blur. With an action selected, the row sets the value the action ends on.

The blur moves from where it stood when the action began to the new value, along the action’s curve. See Set what an action animates to.

With blend modes

A clip with a blend mode blends its averaged picture once. A screened clip, for example, screens its blurred picture over what’s under it.

Where it stays sharp

These draw sharp whatever Motion Blur says, and the row keeps its value:

A clip in a transition, for the frames of the overlap, and every clip inside a nest clip that’s in one.
A clip on a matte track, and the clips a matte cuts.
A clip cut by Text Behind Subject, and the copy of the person it draws.
A clip with a drop shadow.
A nest clip itself. The blur goes on the clips inside it. See Nests and adjustment clips.

Nests and adjustment clips

A nest clip can’t take motion blur, so the row is greyed for it, and for any selection with a nest clip in it. Set the blur on the clips inside the nest instead. They blur when the nest moves.

An adjustment clip has no picture to move. It has no Picture sub-tab, so there’s no row to set.

With an agent

An agent sets the blur with motion_blur in set_video, from 0 to 1. 0 is off and the default, and 0.5 is the row’s 50%. set_action_end sets the value an action ends on, and render_frame draws the blur as an export would.

On a nest clip or an adjustment clip, a value above 0 stops with an error and 0 always goes through. A nest clip’s error reads “clip N shows a nest and cannot take motion blur: set it on the clips inside”. See Tools: picture and grade.