Los Angeles ? Why do moviegoers accept tragedy from the star of “Turner & Hooch” but not from the leading man of “Ace Ventura: Pet Detective?”

Like comedy, it’s partly a matter of timing.

Comic actors who ease into darker characters over a number of years often fare better than those who plunge into drama too quickly. And a clumsy transition from the wacky to the sublime can damage a career by alienating fans.

“Do I think, ‘What will the fans think?’ … I don’t know. I just hope they keep watching,” said Robin Williams, who delivered two sinister performances this summer, as a homicidal writer in “Insomnia” and a lonely stalker in the new “One Hour Photo.”

Despite the risk, Williams, who won a supporting actor Oscar in 1998 for a somber role in “Good Will Hunting,” said shifting from comedy to drama keeps an actor fresh. “You want to find characters that you haven’t seen yourself do and that maybe no one has seen before,” he said.

Few old-time comics such as Groucho Marx or Bob Hope felt compelled to try serious acting, but many contemporary comedians see drama as the key to longevity and influence in Hollywood.

Adam Sandler has put aside his rage-filled comedy for a more tender role in the upcoming “Punch-Drunk Love,” while “Friends” actress Jennifer Aniston has tried to step out of her sitcom’s shadow with the gloomy drama “The Good Girl.”

“Everybody wants to do more than what their core niche skill is,” said Josh Spector, a film writer for The Hollywood Reporter. “It’s the same as TV actors wanting to be movie stars, singers wanting to act and actors wanting to direct.”

Getting a break

Unlike Jim Carrey and Steve Martin, who have had difficulty attracting audiences to their more sedate work, Williams and two-time Oscar winner Tom Hanks are virtual case studies in how to move from comedy to drama.

Like Hanks, who started out in screwball movies like “Bachelor Party” and the cop-and-dog caper “Turner & Hooch,” Williams made a very gradual switch from comedies like “Club Paradise” and “Popeye” to heavier roles in the 1980s.

He played sad characters in the comedies “The World According to Garp” and “Moscow on the Hudson” before shifting to witty characters in the melancholy “Good Morning Vietnam” and “Dead Poets Society.”

From there he took a non-joking role as a doctor caring for comatose patients in 1990’s “Awakenings,” then reversed himself: going from that weighty life-and-death story to the tragi-comic “The Fisher King” and the fantasy “Hook.”

Comedians often make good dramatic actors because the energy they suppress for a serious role can add depth to their performance, said “One Hour Photo” writer-director Mark Romanek.

“Robin was sometimes hysterically funny before a very serious take,” Romanek said. “That was him blowing off steam so the character was stripped of all that. I think audiences can sense he is holding back a volcano and it adds an edge to the character.”

Often, the hardest part for a comedian is just getting the chance to appear in a drama. Producers and studios must be convinced that fans will accept the serious turn.

In Hanks’ case, audiences were used to him in silly projects, including the mermaid love story “Splash,” but his bittersweet comedies like “Big” and “Punchline” showed off his dramatic skills as well. By the early 1990s, Hanks was a back-to-back Oscar winner for playing a terminal AIDS patient in “Philadelphia” and a kind simpleton in “Forrest Gump.”

Audiences have largely forgotten his comic past; Hanks has become progressively more morose with “Saving Private Ryan” and “Cast Away,” building up to his latest and most vicious role as a vengeful hitman in “Road to Perdition.”

Similarly, Woody Allen went from the lighthearted laughs of “Sleeper” and “Annie Hall” in the 1970s to more dour projects like “Crimes and Misdemeanors” and “Shadows and Fog.”

Fans of both kinds of Allen movies, however, have shown little interest now that he has returned to light comedies with “The Curse of the Jade Scorpion” and “Hollywood Ending,” which both bombed at the box office.

Looking for respect

Carrey, after the gross-out antics of “Ace Ventura,” said that moving to dramatic roles like “Man on the Moon” and “The Truman Show” was a bid for respect.

“I think that there is a danger with any comedic artist that at a certain point people sit back and go, ‘Okay, now you’re an old guy and you should have some dignity,”‘ Carrey said late last year while promoting his Red Scare drama “The Majestic.”

But both “The Majestic” and “Man on the Moon” underperformed at the box office, perhaps because the image of Carrey talking with his backside in “Ace Ventura” was still too fresh in moviegoers’ minds.

“Would ‘The Majestic’ have been a hit with an established serious actor? I don’t know,” said Spector, of The Hollywood Reporter. “But Carrey was not selling to his core base of fans who love him.”

Similarly, critics praised Bill Murray’s performance as a man looking for meaning after World War I in the 1984 drama “The Razor’s Edge,” but fans of “Ghostbusters” showed little interest in the soul-searching role.

In recent years, however, Murray has developed a side career with dramatic parts in “Rushmore,” “Cradle Will Rock,” “Hamlet” and “The Royal Tenenbaums.”

Like Murray, comedians who choose smaller roles in serious movies can reap honors without the risk of carrying the entire film.

Martin had little success shedding his wild-and-crazy guy image when he starred in the dramas “A Simple Twist of Fate” and last year’s “Novocaine,” but he was well-received in a supporting role as a high-class con artist in “The Spanish Prisoner.”

Dan Aykroyd’s turn as Jessica Tandy’s blowhard son in “Driving Miss Daisy” earned him an Oscar nomination and other small parts in the dramas “Chaplin” and “Pearl Harbor.”

“These guys have spent so long making people laugh,” Spector said. “And as they get older … this is a chance to experiment without the pressure of being the star.”