Click the control or press R to activate.
The Inner Edge Falloff control, part of the Ring Flare control group, sets the rate at which the intensity of the inner edge of the Ring Flare decreases as it nears the highlight. The inner edge is that portion of the effect which is between the brightest part of the ring and the highlight.
Higher Inner Edge Falloff values make the Ring Flare intensity fall off more rapidly.
Note that, as the falloff is increased, a point will be reached where the inner edge flare will start to appear smaller. This occurs because the falloff setting has reduced the intensity at the inner edge to a level that is too dim to be visible at the current setting of the Intensity control.