Correcting Black Borders Around Your Clip
When the SmoothCam filter compensates for camera movement, it translates, rotates,
or scales your clip in the opposite direction, potentially causing a black border around
the edge of the clip in the Canvas. To correct for the black border, the SmoothCam filter
determines which frame in your clip requires the most scaling to remove the black
borders and then automatically scales the entire clip by that amount.