Just a quick note. There is no directors cut of Dune. There's the theatrical cut, and then there's teh television edit, also known as the Alan Smithee version. It's called Alan Smithee because Lynch had his name removed from that version of the film. Alan Smithee is a name that the Director's Guild has put on films where the director washes his hands of the project for whatever reason, usually studio interference. While the Smithee version is longer, it's purely a TV edit, it could never be presented in the film's original aspect ratio, because the elements used to extend the film were all panned and scanned. Sometimes, they're just shots from the theatrical version, flipped so they look kinda different.

Unless of course we're talking about the Sci-Fi mini series here, in which case pretend I didn't say anything