"It's a good idea," Penn said at the Toronto International Film Festival, where "Into the Wild," his fourth directing effort, played in advance of its Sept. 21 theatrical debut.

The Toronto festival is showcasing a big collection of films by actors turned directors, among them the filmmaking debuts of Helen Hunt, David Schwimmer, Gael Garcia Bernal and Alison Eastwood, whose father, Clint Eastwood, is a paragon for performers who want to make their own flicks.

On "Into the Wild," Penn adapts Jon Krakauer's best-seller about Christopher McCandless (Emile Hirsch), a young man whose bold, two-year trek around North America came to a tragic end in Alaska. Penn, who previously directed "The Indian Runner," "The Crossing Guard" and "The Pledge," said "Into the Wild" has reaffirmed his goal to one day give up acting in favor of directing.

"I've committed to act in a couple of things this year based on directors that I have great admiration for," Penn said. "But yeah, this movie brings me to a place where I know what it is that I'm really looking for in making a decision about what I want to do as a director. So I feel more energized than ever in that way."

What energizes Penn and others to branch out beyond acting?

Some say acting alone gets boring. Some say directing can prolong their film careers in an industry where good roles dry up as actors age. Some say they just want to do it all.

"I want everybody's job, because it's greed for creative control, greed for art," said Tommy Lee Jones, who made his filmmaking debut with 2005's "The Three Burials of Melquiades Estrada" and hopes to direct a new version of Ernest Hemingway's "Islands in the Stream."

George Clooney — who earned a best-directing nomination for 2005's "Good Night, and Good Luck" and returns this fall to direct "Leatherheads," a 1920s football comedy in which he stars with Renee Zellweger and John Krasinski — said taking the reins on a film set gave him a sense of command he lacked earlier in his career.

"Initially, you just get a job. You're thrilled for getting a job. Then suddenly, you start being held responsible for a film that's made. As an actor, you start getting blamed for it if a film sucks," Clooney said. "When I started directing, I started to really like the idea of, you're painting, not just being the paint, and it's your say, and it lives and dies based on what you say. It's interesting and a lot more challenging than acting."

This year already has brought films by such actor-directors as Sarah Polley ("Away From Her"), Ethan Hawke ("The Hottest State") and Julie Delpy ("2 Days in Paris").

Others returning to directing or trying it for the first time in films due out this fall include Oscar-winning filmmaker Robert Redford on "Lions for Lambs," in which he stars with Tom Cruise and Meryl Streep; Ben Affleck on "Gone Baby Gone," starring his brother, Casey Affleck; Denzel Washington on "The Great Debaters," in which he stars with Forest Whitaker; Anthony Hopkins on "Slipstream," in which he also stars; and Peter Berg on "The Kingdom," with Jamie Foxx and Jennifer Garner.

The Toronto lineup features Hunt's "Then She Found Her," in which she stars with Bette Midler, Colin Firth and Matthew Broderick; Bernal's "Deficit," a study of class strife in Mexico; Eastwood's "Rails & Ties," a drama with Kevin Bacon and Marcia Gay Harden; Kenneth Branagh's "Sleuth," with Michael Caine and Jude Law; Frank Whaley's buddy drama "New York City Serenade," with Freddie Prinze Jr. and Chris Klein; Stuart Townsend's "Battle in Seattle," featuring Charlize Theron, Woody Harrelson and Andre Benjamin; and Schwimmer's "Run, Fat Boy, Run," with Simon Pegg, Thandie Newton and Hank Azaria.

Schwimmer, who had directed episodes of his TV sitcom "Friends" and its spinoff "Joey," said actors bring a sensitivity as directors that can be reassuring to insecure performers.

"I was doing a comedy once and came on set for the first day and found the director screaming, chewing out some poor assistant prop person," Schwimmer said. "The tone of the set, you could feel it. The whole crew was on edge. It was a chilling environment, the worst possible environment to go in and try to be funny. Being an actor, you do tend to really take care of the actors and just know what they need."

Actors also can possess a firmer grasp of story and dramatization than directors who have not been in front of the camera, said Jodie Foster, who has directed the films "Little Man Tate" and "Home for the Holidays."

"Very often, the best directors come from having worked inside the industry rather than just coming from film school," Foster said. "Being an actor-director is one of the most effective of all transitions. Very few people in the production end really understand why a scene works and why it doesn't, but an actor does understand that."

Hunt, who directed episodes of her TV sitcom "Mad About You," said it can be uncomfortable giving direction to other actors but that she rarely needed to do much prodding.

"I hired actors who were so good, I loved the few times I was able to say just the right thing to bring an actor to a place that wasn't expected and have him look at me and say, `That felt good.' Maybe I was able to do that because I've been acting so long," Hunt said. "I've gotten so many bad pieces of direction in my life, I know just how painful it can be.

"I felt fiercely protective of the actors, because I've been there, and that probably helped."