Variable Linear Blur filter allows you to control the effect power within the frame. You could have the effect appear only where your subject is rather than over the entire image, or keep the effect in outer areas to softly frame your subject. Parameters: Blur Type "Constant" mode represents the real motion blur effect while "Soft" adds subtle directional blur. One-Way variations add not only motion blur, but a visual motion also. Size Controls the blur power. Value of 1.0 sets the maximum blur, but you can enter in edit field values from -4.0 to 4.0 and get more blur, but with a slightly reduced quality. Negative values set opposite-direction blur for One-Way modes. Direction Controls the blur direction. Value of 1.0 = one full rotation (360 degrees). You can enter values up to 100.0 and create direction animations (rotating direction). Round This option selects the mask shape. If On - the mask is round, otherwise - the mask uses frame aspect. Distribution How the blur size vary over the frame. Values over 0.5 add more blur at frame adge, values under 0.5 - at the frame center. Center X, Y Controls the position of the mask center point. By keyframing the Center control, you can have the effect area track your subject's movement. See also Gaussian Blur variations: Linear Blend - Blur an image and blend with the original. Variable size - control the blur power within the frame with a Linear Mask.