Effects - Center spotEffects - Center spotMasks off a circular area in the center of the picture.
SizeDiameter of the circular mask. Ranging from 0% (no center spot) to 100% (diameter equal to filter diameter).
The soft edge makes the edge between visible and invisible parts less sharp; it makes the edge softer. You can also use the filter setting "Focus" for this, but using a soft edge is considerably faster.
A checkbox which determines which part will be masked off. If
disabled, the center will be masked off, and further effects will
shown only on the outside.
Then the checkbox is enabled, the outside is masked off and further
effects will be shown only in the middle.