When Michael Rogin saw Al Jolson's film "The Jazz Singer," 10 years ago, he was struck by the portrayal of the performer in blackface. The 1927 film tells the story of a son of immigrant Jews who wants to be a popular singer.

When the film was first released, it was common for performers to color their faces and imitate blacks in their shows. Rogin, a political science professor at U.C. Berkeley, was intrigued by the scene in which the main character, Jakie Rabinowitz, sings "Mammy" in blackface to his own mother.

"To see this Jewish immigrant kid singing `My mammy' to his immigrant mother, the disjunctiveness of that," Rogin says.

Jolson's legendary film, which was also the first talking picture, inspired Rogin's latest book, "Blackface, White Noise: Jewish Immigrants in the Hollywood Melting Pot." In it, Rogin examines the sociological implications of Jewish blackface.

"Blackface was the dominant form of popular culture…from the 1830s until 1880. Then it became part of vaudeville and part of motion pictures," Rogin says.

"Though it all played on stereotypes, some portrayals were sympathetic, some hostile." Some of the biggest names behind burnt cork were Jewish ones, according to Rogin.

In addition to Jolson, they included Eddie Cantor, George Burns and Sophie Tucker. For Hollywood Jews, blackface was a way of masking Jewishness, he says.

"In this very Jewish industry, they…thought that depicting Jews would promote anti-Semitism, so they hid it. Blackface is a metaphor for that."

Encountering Jewish blackface was a new experience for Rogin, who grew up in "a Jewish socialist milieu" in Queens, N.Y. Both he and his labor organizer father supported the civil rights movement. As a political science student at the University of Chicago, he picketed the city's Woolworth's during a nationwide boycott that accompanied the Southern sit-ins.

In contrast to the rise in ethnic pride that followed the civil rights movement, early films like "The Jazz Singer" put a positive spin on assimilation.

"They want to recognize the conflict but somehow make you feel that you could have your upward mobility and your shiksa and not betray your Jewish past," he says.

"What's not presented in the movie is that there might be anti-Semitism in the New World. The New World is presented as this place of freedom where you can become a star."

In its rush to sanitize stories for the screen, Hollywood sometimes wrote out their Jewish content. That happened in "They Won't Forget," a fictionalized account of the 1915 lynching of Leo Frank, Frank is portrayed as a Yankee professor instead of a Jewish factory manager.

Jews in Hollywood "were very ashamed of their Jewishness," says Rogin.

He calls the history of Jews and blackface one of moral ambiguity.

"Blackface itself is an unpleasant form which demeans African Americans. There's no way around that fact. Jews were the predominant purveyors of it during the turn of the century. They didn't originate it, they inherited it. A lot of great music came out of that," he says, "but it's based on an exploitive relationship."

Rogin views the phenomenon as the result of Americanized immigrants taking on the myths of the dominant culture.

"Some Jews bought into the dominant racist culture, the myth of the violent or very submissive black, or the supportive, nurturing, unending love that's given by black women."

Even Jewish involvement in the civil rights movement, though noble, had an element of inequality, he says, with Jews speaking for blacks rather than blacks speaking for Jews.

"There was a kind of paternalistic relationship. They [Jews] had more access to money, more authority in society."