Harry Benson believes the fewer handlers a subject has, the better his photos. Reflecting on a 1978 image of Diana Ross jumping in the middle of a Manhattan street, Benson told us he snagged her after asking her to pose in a drugstore. “If that was arranged by a publicist, it would never had happened. She just jumped in the middle of Madison Avenue from a pharmacy there. She enjoyed it. There was nobody around her.” Benson launched his latest book, “New York New York,” with co-author Hilary Geary Ross at a Town & Country celebration at the Hearst tower Wednesday. Also at the party hosted by T & C publisher Valerie Salembier and editor in chief Jay Fielden were Hearst CEO Frank Bennack, among other well-wishers.