On Tuesday, Stuart Craig and Stephanie McMillan respectively earned the ninth and fifth Oscar nominations of their careers for serving as the production designer and set decorator of “Harry Potter and the Deathly Hallows: Part 2.” They shared a win for “The English Patient” in 1996 and this year’s mention is the fourth they have earned for the Harry Potter series, making the Best Art Direction category the place where the franchise (which wrapped itself up in 2011) has seen its greatest Oscar success.

The world of the boy wizard has been the duo’s driving professional task for quite a while. Indeed, Craig (who also won Oscars for “Gandhi” and “Dangerous Liaisons”) is one of the few consistent department heads on the series going back to 2001. He interviewed with “The Sorcerer’s Stone” and “The Chamber of Secrets” director Chris Columbus about the first movie over a decade ago. When he was offered the job, he says he jumped at it and never looked back. McMillan was shortly thereafter called by Craig and agreed to hop on board.

Both noted that they underestimated the popularity of the books when they began work on the series. Craig notes that while two books had been published when he was hired, and they were perceived as hits, the extent of their popularity was not nearly what it is today. “It would have been very intimidating if it already had the worldwide acclaim then as it does now,” he says.

As the films wore on, with subsequent releases of new installments at bookstores, the popularity really took off. Says McMillan, “We knew there were such devoted fans and we had to honor the books as closely as we possibly could.” She did not find that difficult, however, as they provided such rich descriptions and became a constant reference point.

Craig also notes that the books were so descriptive on the looks of places such as Hogwarts and Diagon Alley. “Our responsibility was to place it together,” he says.

At times, the developing story meant they needed to work in particularly new and creative ways. McMillan found the most exciting transformation was turning the Great Hall into the setting of the Yule Ball in “The Goblet of Fire,” for which they were nominated in 2005. “How do we make it into an ice palace,” she reminisces. “Originally we thought silver curtains, silver table cloths and an ice dance floor, but it just went on and on. The drapes man eventually said, ‘Why not just stick the fabrics on the wall?” While an enormous amount of work, the degree of pleasure and pride is palatable in McMillan”s voice. It therefore shouldn”t be surprising that “The Goblet of Fire” earned the duo a trip back to the Kodak after missing for “The Chamber of Secrets” and “The Prisoner of Azkaban.”

For Craig, the final battle of Hogwarts in the latest film was a change he found particularly interesting and challenging. Much more physical space was needed to accommodate all the actors and to create the scope of the battle. In order to realize this, he could not be too faithful to what had gone before. In this vein, he acknowledges that lack of continuity was a concern, but insists that in some sense it was inevitable, because when they started, there were only two books. A set such as the astronomy tower wasn”t needed until (SPOILERS) Dumbledore needed to fall and die from it. “Everybody seemed to accept that each movie had its own integrity,” he says.

McMillan largely agrees with her colleague”s assessment, appealing to an artistic license most moviegoers accept. Considering the fact that the house where Harry”s parents were killed in the first film had to become part of a whole village in the seventh, she says that “if the scene is convincing enough, people accept.”

And for all the changes, they find that much more stayed the same, with McMillan noting that even just in the reusing of sets and props, there was much pleasure. While she was grateful for her large budget, that budget still was not limitless, and integrating places such as a college at Oxford into the world they were designing and building at the studio was a challenge.

Along with the changing story and expanding sets, the duo also had to contend with changing directors. Criag, for one, relished the changes that came with different men at the helm. “Each one of them managed to find a different take,” he says. “It kept the whole thing vital and alive.”

Both comment on the fact that Chris Columbus” strengths lay in working with the child actors, while, Alfonso Cuarón (who directed “The Prizoner of Azkaban,” which signaled the change in aesthetic signature for the series) had a very visual sense. “He wanted to make films much more magical and he really pushed all of us,” McMillan says. They also add that Mike Newell”s film (“The Goblet of Fire”) was really about teenage angst and fun. McMillan says he “liked the boarding school aspect of it” while Craig says the director wanted to inject more humor into the proceedings.

David Yates came on board as the plot of the movies got more serious. “His forte was in emotional, moving drama anyway,” Craig says. But having a single directorial vision on the last four films made the art department’s job, as surely any other department’s, that much easier. Nevertheless, “each film always had plenty of new stuff and new challenges,” McMillan says.

Throughout these changes, however, it should be no surprise that the duo get along fantastically well, as both of them admire each others” tastes. “I haven”t worked with another set decorator in 15 years,” Craig says of McMillan. “I”d be devastated if I had to work without her.” He particularly praises how her very detailed interiors could underline the characters of Professors Dumbledore and Snape on the Harry Potter series.

McMillan, meanwhile agrees that she and Craig rarely fail to see eye-to-eye and that Craig is able to see the big picture and minute details at the same time. “He has the most amazing vision,” she says. “You could ask him about the smallest detail and he”d apply himself to what you want to talk about.”

Other below-the-line personnel were integral in Craig and McMillan’s work, but they changed throughout the series. Craig notes how it is particularly important to have a strong relationship with the cinematographer and the costume designer. “There are obviously color issues to talk about with the costume designer,” he says. “The cameraman tends to start much later,” which can pose a problem as the placement of windows and chandeliers is very important to the cinematographer, and this resulted in sets being redesigned on occasion.

McMillan singles out their relationship with Bruno Delbonnel on “The Half-Blood Prince,” calling it “marvelous” and noting that he had a “very good look.” Indeed, the Academy’s cinematographers branch agreed with her, handing Delbonnel the series’ only cinematography nomination.

Finally, in designing the vault in Gringotts for the final film, there also had to be coordination with the visual effects department. “The physical effects of the floor going down meant we had to work closely together,” McMillan says.

Having spent more than a decade on these films, McMillan most values that she was able to have a 10-year period in which she did not have to “build a reputation” at the beginning of every single film. “It”s different when you don”t know the director and need to build up their confidence in you,” she says. “If you”re the set decorator on Harry Potter, you knew what to do.”

Craig”s views are related in that he was able to build on his work and didn’t have to return to square one every time he started a new film. “Normally things are a one-off affair and 20 years later, you”ll regret a decision,” he says. “On ‘Harry Potter,” we got the chance to hone things and affect things; I”ll certainly take that as a unique experience.”

Craig and McMillan will be contending with four other accomplished design feats this year: Laurence Bennett and Robert Gould”s black-and-white take on Old Hollywood in “The Artist,” Anne Seibel and Hélène Dubreuil”s creation of multiple eras of the City of Lights in “Midnight in Paris,” Rick Carter and Lee Sandales”s WWI-era Europe from “War Horse” and, most notably, Dante Ferretti and Francesca Lo Schiavo”s extraordinary and intricate work on “Hugo.” But even if they go home empty-handed, their work is going down in cinematic history and respect will surely be paid.

Indeed, the Art Directors Guild announced earlier in the season that the Harry Potter series will receive an honorary award for Outstanding Contribution to Cinematic Imagery. Craig and McMillan will be joined by Yates, producer David Heyman and screenwriter Steve Kloves in receiving the honor, which recognizes a truly unique feat, Oscars or not. It’s the first time the award will be given to an entire series of films, and Craig and McMillan’s work is vital key to that consistency of quality.

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