EyeonTips:Manual/Fusion 6/Lens Distort

From VFXPedia

Using the Distortion Map

The distortion map that is produced by this tool contains full pixel coordinates instead of Fusion's usual normalized coordinates (so you should be in float32 mode to start with). To distort an image with it, you need to use the Displace tool. Connect the distortion map to its green foreground input triangle, set the distortion type to XY and put the following expression on both the X and the Y reflection sliders:

1 / Input.Width

This will scale the amount of distortion appropriately so the result looks the same as what the Lens Distort tool would have rendered.