Film buffs ask: Know your noir?

What's in a film noir? There should be dark shadows. An atmosphere of impending doom. And, of course, a femme fatale and a murder or two.

But can you have a film noir if one or two of those things are missing? Good question: As the genre experiences a revival, critics say marketers are hawking lots of old movies as film noir when they don't fit the definition.

The concept of noir has been "diluted," says Eddie Muller, a leading author on film noir. "I will chuckle at what I see people try to pass off as noir."

For instance, a number of online commenters noted that there's no femme fatale or gunplay in 1947's "Daisy Kenyon," a dark, romantic Joan Crawford flick that film buffs consider to be a "woman's picture." Yet the Fox studio declared the Otto Preminger-directed movie to be a film noir upon its release on DVD earlier this year.

Three more 1940s Fox films appeared on DVD under the noir banner last summer, prompting a New York Times critic to complain that the films actually belong in other categories. "I know [noir] when I see it," declared Dave Kehr, with a nod to the Supreme Court judge who famously used the phrase to describe indecency.

The argument over film noir isn't new: It's gone on for decades since the popularization of the French term for "black movie" to describe hard-boiled American films of the 1940s and 1950s, including such classics as "Double Indemnity" and "The Maltese Falcon."

In recent years, the genre has spawned more debate as film noir has grown in popularity.

Several film festivals around the United States honor the film noir genre each year, and the largest – Noir City – attracted sellout crowds a year ago to San Francisco's legendary Castro Theatre. They came despite (or perhaps because of) the festival's focus on films that few audience members had ever seen.

Meanwhile, the Fox and Warner Bros. studios regularly release 1940s and 1950s films noirs on DVD, complete with documentaries and commentaries by the likes of author Mr. Muller, who's known as the "Czar of Noir."

Muller says the films remain relevant because their cynicism and strong, independent women seem modern. "People who would never think to watch a musical, 1940s Western, or war movie will go see a film noir," he says. "They still have a style that people really respond to."

Is it possible to develop a workable definition of a film noir? In general, says Devin Orgeron, associate professor of film studies at North Carolina State University, films noirs "tend to be urban; the plots tend to be convoluted; the distinctions between good and evil are often quite blurry; there is often a duplicitous female character at the center of the narrative; and, of course, [there's] the darkness!"

For his part, Muller thinks noir movies "are stories in which the audience is asked to empathize with a protagonist who is willfully doing something wrong."

But the definition isn't written in stone. "It's a kind of amorphous category," says James Naremore, professor emeritus of communication and culture at Indiana University. "There are certain films that everybody would agree are films noirs, but if you tried to generate a definition based on those films you'd leave a lot of films out."

The classic "Laura" of 1944, for example, seems to have plenty of film-noir trappings – except a femme fatale. (Although some argue that the dearly departed Laura herself fits the bill.) Other so-called noirs lack overt violence or take place in unusual settings.

The debate over noir is a centerpiece of the Noir City film festival, which regularly includes movies that stretch the definition of the genre. This year's festival included 1949's "Reign of Terror," which Muller describes as "the French Revolution as a noir gangster story," and 1943's "The Hard Way," a hard-to-define melodrama starring Ida Lupino and lots of unnoirish singing.

"I suspect in some ways I'm partially to blame by using the term [noir] to direct a spotlight on lots of old films, not all of them bona fide noir, that might otherwise have been forgotten," festival organizer Muller told a film-noir conference in Baltimore in October.

But he doesn't have regrets. "I've played up the argument [over noir] and have consciously programmed films to ask the audience: What do you think?" Muller says. "The debate is lively, and I think it's terrific. How often do people actually discuss the minutiae of modern popular art in this way?"

In the big picture, Mr. Naremore says, the definition of the genre may be unimportant. "Even if we never had the term 'film noir,'" he says, "we'd still be watching these old movies because they're pretty interesting."

Muller puts it this way: "I love all the movies whether they're noir or not."