|Motion Blur applies a blur to objects in motion proportional to their change in position, scale, or rotation over time.
Motion Blur is visible when added to any layer that has been animated with Move & Transform. Move & Transform uses keyframes to specify the properties of a layer, namely its position, scale, or rotation values at a specific time. When more that one keyframe for any property has been placed onto a layer, the layer will smoothly animated between keyframed values over time based on the selected easing curve.
Figure 1: Move & Transform Panel with two position keyframes visible.
Because the effects of Motion Blur are generated automatically based on the movement in the scene, it's often possible to set it and forget it. In cases where tweaking is required, the following settings are available.
Figure 2: Tune 1.00 vs 3.00
Tune: This numerical value corresponds to the size of the blur present on the layer. The default value is 1.00, which is the difference in position, scale, and/or angle between two concurrent frames in an animation. Higher values exaggerate the blur, with 2.00 giving double the amount of blur of 1.00. Lower values lessen the effect.
Position: This toggles motion blur for position keyframes. The default value is On. If set to Off, motion blur will not appear when the layer moves.
Scale: This toggles motion blur for scale keyframes. The default value is On. If set to Off, motion blur will not appear when the layer changes size.
Angle: This toggles motion blur for angle keyframes. The default value is On. If set to Off, motion blur will not appear when the layer rotates.
Motion blur can look far more natural if the easing curves are changed from linear to something where the layer is moving slowly near the beginning and end of the motion. Easing curves can be changed in with Move & Transform. Note that you must place the playhead on the timeline between two keyframes in order to see and alter easing curves.
Figure 3: The easing curve between the keyframes directly left and right of the playhead.
Practical Uses of Tune
The value of Tune directly corresponds to the amount of blur applied to an object, and is based on the difference in position, scale, and/or angle between an object over two concurrent frames. There are a few cases where changing this value may be beneficial. For example, if your project's frame rate is 60fps, but you want to make it look like it is 30fps, you can set the Tune value to 2.00, which will double the blur, making it look like it has half the frames, i.e. 30fps. The opposite is also true. Setting Tune to 0.50 will make a 30fps project look more like a 60fps one.
Order of Effect Application
Motion Blur combines differently with different effects. Effects that do not change the shape of an object, such as Oscillate, which just causes an object to move, will be applied earlier, and will exhibit the effects of Motion Blur as normal. However, effects that change the shape of an object, such as Fractal Warp, will be applied later, which may result in the effect of Motion Blur not being as expected or visible on screen.