1. Change the field of view in your profile .ini (I won't go into detail as there are guides for this online)
2. Go in game with any character possessing a compass
3. Open the map screen (M) and try to move the compass around
4. If your FOV is higher than default the compass will "react" (cursor changes) when the cursor is closer to the center of the screen
5. If FOV is lower than default the compass will react when the cursor is closer to the edges of the screen