By default, DVDFab sets the default output size for DVD copying to DVD5. If you are using dual layer discs, this setting will not give you the quality you are looking for. You can change the default setting and get a truer backup copy of the DVD by following these steps:
1. Open DVDFab.
2. At the top of the DVDFab window, click the left most button (the one with a sun on it).
3. Select Common Settings.
4. In the left pane of the Common Preference window, select DVD to DVD.
5. At the top, click on the Default output size dropdown and select DVD9.
6. Click OK.