Originally posted by: Jagdlieter
What are garbage mattes?
What are garbage mattes?
Read this.

Also, if your television is calibrated to the correct standard, you should not see the mattes at all on the discs. One reviewer mentioned using the above shot from "The Film Formerly Known as Star Wars" to set your "Brightness" or "Black Level" control. Once the matte disappears, you have the correct setting.
Neil