Fanboys fueled a solid if not stellar start for Disney’s 3D “Tron: Legacy,” with an estimated $43.6 million from 3,451 locations, of which 2,424 were 3D-equipped, including 234 Imax runs. “Tron” easily outdid Warner Bros.’ “Yogi Bear” but will need to broaden its demo base to maintain momentum throughout the holiday season.

“Yogi Bear” rang in at an estimated $16.7 million at 3,515, including 2,011 3D runs, falling in line with weekend projections.

The pre-Christmas weekend historically sees modest biz — the frame was down 3% vs. last year — but often comes with higher multiples through the holiday sesh. Though, as one studio exec noted, “Who wants to wait 10 days to find out if their movie is a hit or not?”

Sony’s James L. Brooks-helmed “How Do You Know” is unlikely to recover from its dismal $7.6 million opening, according to most B.O. pundits. The film, which played mostly to women over 30, was budgeted at $100 million and received a C- CinemaScore rating.

Other adult-skewing titles, including Paramount-Relativity Media’s “The Fighter” and Fox Searchlight’s “Black Swan,” had terrific showings in their first week of wide release.

“The Fighter” tallied an estimated $12.2 million at 2,503, after last weekend’s strong per-screen average of $75,000 from four locations. Cume is an estimated $12.6 million. “Black Swan” also figured in the top 10 this week, with an estimated $8.3 million from 959 locations for a cume of $15.7 million.

Overseas, Disney bowed “Tron” in 26 markets, where the film played tops with an overall estimated $23 million from 3,832 runs. In Japan, “Tron” glowed, taking an estimated $4.7 million. Pic’s Japanese take, drawn from an audience that was 70% men, marks a sizable start in the territory, where women make up the majority of moviegoers.

While earning the No. 1 spot in every other market, “Tron” saw just-OK results in Australia with $3.4 million and an even less enthusiastic response in Spain, contributing $1.9 million.

Twentieth Century Fox’s “The Chronicles of Narnia: The Voyage of the Dawn Treader” still managed to secure top coin internationally, adding just under $30 million in its second outing to pic’s total gross of $124.4 million. “Dawn Treader” expanded to Germany and Italy, where adverse weather affected the weekend B.O. Germany was the top territory for “Dawn Treader,” with $3.2 million, followed by Italy’s $2.1 million weekend gross.

While “Tron” and “Yogi Bear” had to compete for a limited number of domestic 3D screens — it was the first time two wide 3D releases have launched during the same weekend — both pics managed to claim better-than-average shares from the format. “Tron” earned an overwhelming 82% of its weekend gross from 3D, boosted by fanboy appeal and 234 3D Imax runs, while “Yogi Bear” saw 57% from 3D, slightly higher than Disney’s “Tangled.”

“Tron” earned nearly 25% of its weekend gross from Imax, for the exhib’s largest opening share ever, with $10.3 million: Imax per-screen average was $44,000. Pic’s Imax take even beat the $9.5 million bow for “Avatar,” though it launched at 55 fewer Imax theaters.

“Disney’s ‘Tron’ and the Imax experience easily packed a powerful one-two punch this weekend,” said Imax prexy Greg Foster. “We’re confident that the eventizing of the film in our theaters will continue through Christmas and the month of January.”

With new (“Gulliver’s Travels”) and existing (“Dawn Treader,” “Tangled”) 3D fare in the marketplace, “Tron” will continue to hold on to the same number of Imax runs. “Yogi Bear” will have to compete for available 3D screens in regular multiplexes.

“Tron” received a B+ rating from moviegoers, with 73% age 18 and over. During the next few weeks, the PG-rated sci-fi tentpole is expected to broaden beyond its fanboy core, said Disney prexy of worldwide distribution Chuck Viane.

“To open at this figure positions us nicely over the holidays,” Viane said, explaining that “Tron” could play strongly for several more weeks.

A prime example of a high multiple is “Avatar,” which bowed this weekend last year to $77 million (lamented by some B.O. pundits as a soft opening) but became a four-quadrant film that eventually grossed a record $2.7 billion worldwide.

Meanwhile, Warners’ “Yogi Bear” was given an A- rating from moviegoers under 25, who accounted for 52% of the weekend aud. Jeff Goldstein, Warner exec VP of domestic distribution, described the film as a “nag and drag” pic, benefiting primarily from kids and parents on vacation over the holidays.

According to Goldstein, about 60% of students will be out of school today. “It’s not necessarily how the film opens, but how it plays,” he said.

With “Yogi” entering the market, Fox’s 3D family title “Dawn Treader” saw a better-than-expected hold, dropping 48% in its second frame for an estimated $16.7 million. “Dawn Treader” opened soft last weekend domestically, but it’s showed signs of resilience with a Stateside cume of $42.8 million.

Elsewhere on the adult front, both “The Fighter” and “Black Swan” drew aud awareness from last week’s Golden Globes and SAG nominations, with the latter set to expand even wider next week.

Par vice chairman Rob Moore described “The Fighter” as the kind of movie that plays with six- to seven-times multiples. He compared “The Fighter” to Par’s “Up in the Air” last year which grossed $3.2 million during its first week of wide release and wound up totaling $83.8 million.

Moore credited producers David Hoberman and Todd Lieberman, along with star-producer Mark Wahlberg, and noted that Relativity Media brought on helmer David O. Russell.

Sony’s “How Do You Know” likely fell victim to “The Fighter” and “Black Swan.” Pre-weekend tracking pointed to more definite interest among women for “Black Swan” than for “How Do You Know,” while “The Fighter” skewed 53% female.

Sony distribution exec Rory Bruer described the launch as “a tough way to end the year, because we’ve had such a great one.”

Brooks pics usually open to modest results; “Spanglish” bowed to $8.8 million in 2004 and cumed $42.7 million domestically. A similar result for “How Do You Know” would still fall significantly behind the pic’s estimated cost. “We’re disappointed,” Bruer admitted. “Everybody worked really hard on this film, and we hoped for more.”

Pic even landed behind Sony’s soph sesh player “The Tourist,” whose weekend estimates tied with those for 3D toon “Tangled,” both at $8.7 million. Stateside cume for “The Tourist” reached $30.8 million, while “Tangled” has played nicely with $127.8 million.

In limited release, Lionsgate’s Nicole Kidman starrer “Rabbit Hole” bowed at five locations in New York, L.A. and Toronto, with a decent $11,000 average and a weekend total of $55,000. Lionsgate will expand the film to the top 18 markets Christmas Day.

ATO Pictures’ “Casino Jack,” earned less per screen, with an average of $5,000 at seven U.S. locations for a total estimated $35,000. Biopic about Jack Abramoff, played by Globes nominee Kevin Spacey, widens next weekend to Washington, D.C., San Francisco and Denver.

Meanwhile, the Weinstein Co. continues its slow platform release of “The King’s Speech” to 43 locations, up 24 from last weekend, averaging a royal $25,000 per screen, with a total of $1.1 million. Pic has cumed $2.9 million.