“Avatar” and “The Hurt Locker” had come into the night as favorites, but the smaller film took the prize from the bigger in the end. 

“There’s no other way to describe it, it’s the moment of a lifetime,” said Ms. Bigelow in accepting her award. It was presented by Barbra Streisand, who announced it with the words, “Well, the time has come.”

Mark Boal, a producer of “The Hurt Locker,” said of his modest expectations when the movie was shot back in 2007, “Hopefully, we would find a distributor and somebody might even like the movie.” 

There was no mention of a last-minute embarrassment in which a fellow producer of the film, Nicolas Chartier, had been banned from the show for violating Oscar rules by urging academy members by e-mail messages to vote against a film assumed to be “Avatar,” which had the advantage of a vast budget and enormous popularity.

In a sense, the awards season had shaped up into a showdown between James Cameron, who directed “Avatar,” and Ms. Bigelow, who was previously married to Mr. Cameron. 

Among other winners, Christoph Waltz took best supporting actor at the start of a sluggishly paced ceremony for his bilingual performance as a Jew-hunting Nazi officer in “Inglourious Basterds.” And also, as expected, Mo’Nique won for best supporting actress for her portrait of a terrifying mother in “Precious: Based on the Novel ‘Push’ by Sapphire.” With no excess of modesty, Mo’Nique thanked the academy’s members for showing that “it can be about the performance, not the politics.” The remark was a reference not just to her considerable talent, but to the fact that she had refused to spend time playing the usual Oscar campaign game. Backstage, she blamed the media for trying to stir up a controversy. 

Jeff Bridges, a multiple nominee and now first-time winner, took best actor for his gritty portrayal of a broken-down country singer in “Crazy Heart.” A darling of the Hollywood crowd, Mr. Bridges had been seen as the designated winner almost from the moment Fox Searchlight made a last-minute decision to drop the low-budget movie into the Oscar race. “Thank you, Mom and Dad, for turning me on to such a groovy profession,” said the gray-bearded Mr. Bridges, who brought the crowd to its feet in a prolonged ovation as he whooped, hollered and showed obvious joy in the moment.

“Crazy Heart,” one of the evening’s smaller contenders, also took an Oscar for its theme song, “The Weary Kind,” by Ryan Bingham and T Bone Burnett.

Sandra Bullock, who had been pointed toward an Oscar since winning a bellwether Screen Actors Guild award, won best actress for her performance as a tough and loving contemporary Southern mother in “The Blind Side.” Like Mr. Bridges, she was clearly a favorite of those in the auditorium, though she had never been nominated before and had been best known for romantic comedies like “The Proposal” and the occasional action film, like “Speed.”

“Did I really earn this, or did I just wear you all down?” Ms. Bullock asked her cheering peers.

“Up in the Air” was shut out, although the movie, about a corporate operative who specializes in firing people, had propped up the long awards season with appearances at various prize ceremonies on both coasts and in England by George Clooney, its star, and Jason Reitman, the writer-director. 

The show clocked in at a relatively long three hours and 32 minutes, but at times it felt longer than it actually was. That was mostly because the first half was loaded with clip samples and retrospectives, while the latter part moved along with the speed that one of its producers, Bill Mechanic, had promised in advance.

Before the bigger awards were announced, there was a trip back to “The Dark Knight,” as Morgan Freeman explained how sound editors handled a movie from an earlier year, and a lengthy string of excerpts from horror movies, in an effort to reach fans who do not find movies like the “Twilight” series on the show.

The pace had already slowed with the screening of highlights — and the introduction of two recipients, Roger Corman and Lauren Bacall — from an honorary-awards ceremony that had been moved off-camera to a November date, precisely to keep the show from slowing. 

This came only a few minutes after a narrator took time to read chunks of script over clips from the best adapted screenplay nominees. But Geoffrey Fletcher, a first-time nominee who won for “Precious,” put some heart in the proceedings as he gasped and seemed to weep in accepting. “I thank everyone,” Mr. Fletcher said simply.

Going into the evening, Mr. Cameron’s 3-D blockbuster, “Avatar,” was expected to dominate the evening along with the smaller, intense film “The Hurt Locker.” 

But it was not until nearly halfway through that “Avatar” won its first award, for art direction. It was presented by Sigourney Weaver, one of the film’s stars, who sounded relieved as she opened the envelope and spoke the film’s title. Awards for cinematography and visual effects followed. But “The Hurt Locker” had already won for its original screenplay, sound editing and sound mixing, and later added one for film editing, ending any thought that Hollywood’s behind-the-scenes types might have rallied behind “Avatar.”

For most of the night the ceremony put in sharp relief a split between the 5,777 voting members of the Academy of Motion Picture Arts and Sciences, who in many categories continued a recent tradition of honoring small, independent-style movies, and their own broadcast, which played heavily into the big movies.

Ms. Bullock, from a crowd-pleaser, “The Blind Side,” took the stage as a presenter and was the subject of congenial jokes about her career, which has been heavier on commerce than art, with movies like “The Proposal” and “Miss Congeniality.”

“Avatar,” meanwhile, was a constant presence. Ms. Weaver, Zoë Saldana and Sam Worthington, the film’s stars, were all presenters. From an Oscar stage that was bathed in blue for most of the night, presenters and hosts aimed quips at Mr. Cameron, who had a Na’vi blue kerchief (a reference to characters in “Avatar”) in the pocket of his tuxedo and generally traded on the film’s vast popularity in a clear bid to hold viewers, even as the prizes were sprinkled among other films, many of which had made only a small mark at the box office.

The best documentary feature award, presented by Matt Damon, went to “The Cove,” a film that exposed the slaughter of dolphins in a Japanese village. The best foreign language feature, presented by Pedro Almodóvar and Quentin Tarantino, went to “The Secret in Their Eyes” (“El Secreto de Sus Ojos”) from Argentina.

Mr. Boal’s original screenplay for “The Hurt Locker” made an expected mark for that film. In accepting the prize Mr. Boal talked of his experience as a war correspondent, and dedicated the Oscar to troops in Iraq and Afghanistan.

In more of a surprise, Geoffrey Fletcher won the award for best adapted screenplay for “Precious.”