I've seen a lot of films set during the French Revolution, and this odd and tiresome effort by Eric Rohmer is definitely not one of the better ones. I can't help but feel that Rohmer had some grand vision for this movie, as recreating the life and vision of some late 18th century aristocrat, and he did not entirely succeed. For starters, the film seems less 18th century and more like a late 19th century stage play- filmed in the style of an early silent film, circa 1915. One almost expects the actors to begin to gesture wildly and start rolling their eyes. Character development is non-existent, and the direction, with its paucity of camera angles, is nothing to write home about. The actors do the best they can, but there is only so much that they can do, given the clunky script and direction. I didn't find the film to be boring exactly... just odd and half-baked. The much-ballyhooed digital backgrounds add to the air of weird, never-never land detachment to the entire proceedings.
All in all, this is not the worst movie I've seen, but if you really want to get into the mindframe of 18th century nobility, then I would highly recommend the 1999 Masterpiece Theater miniseries "Aristocrats," which is far more entertaining, convincing and involving than "Lady and the Duke." If you wish to see a great film about the French Revolution, then go see "La Révolution Française" with Jane Seymour and Klaus Maria Brandauer (if you can find it), or "Danton" with Gerard Depardieu. Even the 1938 "Marie Antoinette" is more interesting than the Rohmer film, and Norma Shearer's reaction to the Princesse de Lamballe's head is a great deal more powerful than Lucy Russell's.