Size controls the blur radius. The larger the size, the blurrier the screen will become. It is measured in pixels. By default, this value is 24. Although this value is a float and can be set without being clamped, only integer values in the range [0, 56] will produce a change.
BlurEffect/Size|Size = 0 (or no BlurEffect at all):
BlurEffect/Size|Size = 10:
BlurEffect/Size|Size = 50: