The Blur group effects

The blurs are often used to hide faces in recorded animations. Sometimes, they are also used to create artistic effects.
In order to study the effects of the Blur group, we will use the two pictures below : a photo and a drawing.

The photo
The drawing

Independent of which blur effect you will choose, don't forget it will be controlled by the FX Stack keyframe system.
A recorded video sequence can also become gradually blurred in time.