Mildred Pierce Mildred Pierce

She's won an Oscar. She's starred in one of the most successful movies of all time. Now, Kate Winslet is about to conquer another first: television.

"It never occurred to me, beyond the moment of reading those scripts, 'Wow, this is television, therefore it's going to be different somehow,'" Winslet said Friday at the Television Critics Association's winter preview sessions. The actress is starring in HBO's 5-part adaptation of Mildred Pierce. "Sure we have more to shoot ... but the level of determination and level of focus was so much more intense than certainly any film I've ever been apart."

Evan Rachel Wood, Guy Pearce join Mildred Pierce remake

In Mildred Pierce, based on the 1941 novel by James M. Cain, Winslet will play a single mother struggling obsessively to win her daughter's love during the Great Depression. It's her first role since nabbing the 2009 Oscar for her performance in The Reader. Evan Rachel Wood and Guy Pearce also star.

The 35-year-old actress continued that she found television a bigger challenge than film.

"Film, schmilm — I'm telling you television is so much harder," Winslet said. "It didn't affect the work ethic in any way other than we had more story to tell, which was a luxury, and less time to work to that goal. But that just meant we were hyper-focused."

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Winslet is not the only one making her first transition from the big screen to the small screen. Mildred Pierce also marks the first television project for Academy Award-nominated screenwriter Todd Haynes (Far From Heaven), who directed the miniseries. "This was a marathon experience. it was great to share it with film people. It was new for all of us. New for Kate, new for Evan, new for Guy," Haynes said [Editor's note: Wood was a series regular on the ABC drama Once and Again from 1999 to 2002]. "We walked into it with the kind of demands that we bring normally."

Although Haynes said the miniseries required more shooting packed in a relatively tight schedule, he compared working with HBO to working with Hollywood's major film studios. "I really felt the incredible support of HBO constantly and daily and that really did help us," Winslet added. "It was incredibly intense for all of us. But I felt we had this glorious cushion... They were really there for us."

Mildred Pierce debuts on Sunday, March 27 on HBO.