This effect differs from Blur only in
that you can change a matrix of weight coefficients and do a
directional blur.
For example if this matrix is used
0
0
0
5
10
5
0
0
0
the blur will be carried out on a horizontal plane.
The effect is applied to the image as you move the slider and
you can see the effect in the
edit area and panel of properties
of the object. Press Apply button to make your changes permanent.