'Lincoln's' Sally Field on Becoming Mary Todd Lincoln (Video)

Sally Field has played many great women throughout her career, and it turns out that it isn’t always easy for her to leave those characters behind.

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Field plays Mary Todd Lincoln in Steven Spielberg’s Lincoln, which follows Abraham Lincoln (Daniel Day-Lewis) as he fights to get the 13th Amendment passed, while dealing with a tumultuous relationship with his wife and a strained one with his eldest son, Robert (Joseph Gordon-Levitt).

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While Day-Lewis is known for his method acting, staying in character for the duration of a film shoot, Field tells The Hollywood Reporter that she works the same way.

“I’ve always stayed in character, every film that I’ve ever done that I’ve played any kind of weighty important person, I never come out of character,” she says.

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Mary Todd Lincoln is a complicated woman in the film, struggling with debilitating migraines and mourning the loss of her young son Willie. She’s also a firecracker who gets into a verbal jousting match with a rival, Republican Thaddeus Stevens (Tommy Lee Jones), and also has a powerful fight with her president husband in a memorable scene between Field and Lewis.

“People have this idea about Daniel and how he works, but it is OK because Daniel has the position and brilliance and power to be able to let it be known and let it be out there that the crew understand it and respect it,” she says.

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“I’ve always worked like that but I’ve always felt that I had to hide it,” she says.

To play Mary, Field did extensive research, reading biographies and even visiting the first lady’s hometown of Lexington, Kentucky. She also gained 25 pounds for the role, working with a nutritionist to add the pounds to her petite 5'3" frame.

“We wanted Mary’s dimensions to be relatively the same that her real dimensions are,” Field says.

While she has since shed the extra weight, Field admits to THR that it takes her a long time to let go of a character, if she ever really does.

“It took me a long time to actually shed Mary,” she says. “But I think there will be something always, always there that remains linked to her.”

Watch THR’s full interview with Field above.

Lincoln, currently in limited release, opens wide on Nov. 16

Email: Rebecca.Ford@thr.com; Twitter: @Beccamford