Among the stars of any period drama are the costumes, and with “;The Duchess,”; costume designer Michael O'Connor knew his work would be held to even greater scrutiny. He was, after all, creating a wardrobe worthy of Georgiana Cavendish, the Duchess of Devonshire, a woman defined, like her 18th-century contemporary Marie Antoinette, by her exaggerated sense of style.

Keira Knightley plays the duchess in the film slated to open tomorrow, and 27 costumes were made for her, another 15 for her rival Lady Elizabeth Foster, played by Hayley Atwell, and 12 for Ralph Fiennes, who plays the Duke of Devonshire.

While it would have been tempting to go overboard with fashion, a la “;Sex and the City,”; O'Connor veered toward restraint.

“;(The duchess) was very fashion-aware, and once you've shown that, you don't have to do it all the time,”; he said, by phone from London where he is enjoying a break between projects. The duchess' stature as a tastemaker is conveyed in a few scenes, such as a grand ballroom entrance, in which she astounds guests with a towering feathered headdress. A later party scene showed women had adopted the feather look, but by then, like any fashion leader, the duchess had moved on.

What makes any costumer's task difficult is that nothing can be stitched until set details are established. In film, no piece stands alone. Every piece of fabric must work with specific scenes to avoid the noise of background tapestries or having extras in crowd scenes distract from the leads.

“;There are many different stories going on simultaneously, so I'm trying to say something with the costumes about the characters in the scene,”; said O'Connor, whose recent credits include “;The Last King of Scotland,”; “;Brick Lane”; and “;Miss Pettigrew Lives for a Day.”;

He said that in learning about the duchess, he knew he wanted to contrast the tumult of her personal life versus the polished veneer of her public persona, a concept familiar to contemporary audiences fed a steady diet of crash-and-burn celebs.

In the film, the duchess is depicted as the “;It girl”; of her day, cultivating public infatuation with celebrity to help usher in sweeping changes to England as a leader of the forward-thinking Whig Party, while also advocating for women's rights.

But her image was at odds with her personal life and rocky marriage to William Cavendish, fifth Duke of Devonshire, made worse by her inability to quickly produce a male heir. Georgiana has often been compared to Princess Diana, one of her descendants.

One of the duchess' costumes was based on a portrait of Marie Antoinette, and O'Connor sympathized with the two women. “;They were landed gentry who did very little by way of earning a living, so they did everything to excess—drinking, gambling. There was a demand to read about them in the gossip columns, same as today, so there was pressure to keep up appearances, even through miscarriages and all that was happening.

“;I think people watching the movie do get a sense of its relevance today, so it doesn't seem like a film stuck in the past.”;