Mary Ellen Mark photographed these teen-agers one summer day a few years ago, at the Brighton Beach end of Coney Island, because she found them “seductive—innocent but not innocent.” Like Tiny, the fourteen-year-old prostitute in Seattle who is the subject of one of Mark’s most famous images, the two girls on the right confront the camera head on, almost defiantly. They seem convinced of their attractiveness, and not bothered by the anomalous juxtaposition of their natural beauty with the broken sidewalk and graffiti, the skimpy bra tops and cutoff jeans. Aplomb, or a brace attempt at it, in an impoverished landscape is one of the themes of “Mary Ellen Mark: American Odyssey,” a retrospective of the photographer’s work from 1963 to 1999 that is now at the uptown branch of the International Center of Photography. (It is the final show at that location, which is about to become a grand private house again.) Mark is following Walker Evans, Robert Frank, and Diane Arbus, who also made odysseys through America. They found poor but noble farmers, melancholy waitresses in diners, and various freaks. Mark finds the inmates of a mental institution, transvestites, a club of obese women, white supremacists, children with guns, and drug-addicted parents. This is, as she writes in an Afterword to the show’s catalogue, “grim” subject matter, ”on the edge of or outside the mainstream of our culture,” but the best of the work—for instance, the sad sequence of pictures of Tiny’s family in Seattle, taken over a period of years--is leavened with an un-Arbus-like compassion. Last month, Mark received I.C.P.’s second annual Cornell Capa Award for distinguished achievement. The first one went to Robert Frank.