Costume designer Trish Summerville, who has previously worked with David Fincher on “The Girl with the Dragon Tattoo” and “Gone Girl,” says she was very excited when she learned the director wanted to do a full project in black-and-white. The only time she had ever tackled crafting costumes was in flashback sequences, not a full-length feature. And who better to do it with than Fincher?

In “Mank,” Fincher takes audiences back to the golden age of Hollywood as screenwriter Herman J. Mankiewicz (Gary Oldman) sets out to write “Citizen Kane.”

Summerville says her approach was “learning what his [Fincher’s] perception of black-and-white was. We had information to move forward with, but it was really him zoning in on exactly what that was going to look like and exactly how he was going to light it.”

Additionally, Summerville had an advantage — she was recreating looks based on real-life people and had access to a lot of photographs and source material. That was particularly true of Marion Davies, played by Amanda Seyfried.

One look was inspired by a photograph Summerville saw of Davies posing in front of a car. In the photo, Davies is standing next to the running board of the car, wearing a coat with a silver mink fur collar. Summerville found a perfect moment to recreate the coat for a scene where Davies is leaving MGM Studios.

The coat was crafted in a muted powdery blue, using a pale dusty periwinkle wool crepe. The fur used in the film is faux to mimic a minx, and Summerville painted it to give it more depth.

“He graciously put on 15 pounds for ‘Mank,'” she says of Gary Oldman, who played the titular character. Since the film took place over a period of time, she used his waistline and how high he wore his pants to show the passing of time. “We go from the ’30s to 1942 with him, so as he got older, the trousers got lower and lower under his belly.” The addition of suspenders helped frame Mank’s belly.

Summerville notes Mank wasn’t the most stylish of men. She says, “He would have saved his best suit for a funeral or a wedding, so that’s why we have his nicest suit and most pulled together at the funeral.”

Over the years, Summerville says she has learned about Fincher’s authenticity to a project and script. “A lot of his stuff is so timeless. The thing I learned from him is how to really show the life in the characters and keep things very authentic and entertaining while staying very true to the character.”

Watch the full interview with Summerville below.