“The Dark Knight,” the last completed film of late actor Heath Ledger, is nearing its release and the cast is full of praise for Ledger’s portrayal of the Joker, even saying the performance deserves an Academy Award.

Christian Bale dons the trademark bat suit once again while Chris Nolan returns to directing duties for “The Dark Knight,” sequel to 2005’s “Batman Returns.” Villains are a-plenty in the new installment, the most notable being Heath Ledger’s Joker.

Fellow cast members Gary Oldman, who portrays Lieutenant James Gordon, Aaron Eckhart, who gives life to Harvey Dent / Two-Face, Bale and Nolan were promoting the film, to be released July 18, this weekend, and talked admiringly about Ledger’s work.

Oldman told E! Online Ledger “had this frequency none of us could hear” and opined that “the Academy tends to overlook movies like this, but this acting is so good it’s going to be very hard for them to avoid it.”

Eckhart also said Ledger “definitely” deserves an Oscar, while Bale commented that the Australian actor has “raised the bar.”

Nolan was most explicit in detailing Ledger’s devotion to his character. “He called me during preproduction from time to time to tell me what he was working on,” Nolan said. “He told me he was researching the way ventriloquist dummies talk. It was a bit peculiar.”

Ventriloquist dummies were only part of the recipe Ledger put together to portray the Joker, along with influences from Stanley Kubrick’s “A Clockwork Orange” and Charlie Chaplin, per E! Online.

The effect Ledger was striving for, Nolan ultimately discovered, was a vocal style as chaotic and erratic as the Joker’s inner world.

Should Ledger receive a posthumous Academy Award, it would be the second such event, following Peter Finch’s win for the 1976 movie “Network.”

“The Dark Knight” co-stars Michael Caine as Alfred Pennyworth, Morgan Freeman as Lucius Fox, Maggie Gyllenhaal as Batman’s love interest Rachel Dawes and Cillian Murphy as Dr. Jonathan Crane / Scarecrow.

The end credits pay a fond tribute to Ledger, as well as to special-effects technician Conway Wickliffe, who was killed last September in a stunt-car accident. The tribute reads, “In memory of our friends Heath Ledger & Conway Wickliffe.”