For everyone making a legitimate backup copy of your purchased DVD content, cough cough, I have a suggestion.
I see a lot of people using DVDShrink or DVD2OneX (under Windows and MacOS respectively) to shrink dual layer DVD’s to the easier-to-find 4.7GB variety. Invariably they select the entire content of the DVD and shrink it, causing a quality reduction ranging from 40 to 70%.
Figure out what you’re going to use the single-layer copy for. Do you need the extra features, or the menu, or the music tracks, or foreign languages? If you don’t, unselect them. Your typical main feature component of a DVD is only 10% larger than the 4.7GB available, which means you’ll be able to retain 90% of the quality of the original.
Have a nice day.