“A photograph is a secret about a secret,” Diane Arbus said. In the case of Vivian Maier, the photographer was a secret, too. From the nineteen-fifties until a few years before she died, in 2009, destitute at the age of eighty-three, Maier took at least a hundred and fifty thousand pictures, mostly in Chicago, and showed them to nobody. It’s telling, perhaps, that one of her favorite motifs was to shoot her own shadow. For decades, she supported herself as a nanny in the wealthy enclaves of the city. But her real work was roaming the streets with her camera (often with her young charges in tow), capturing images of sublime spontaneity, wit, and compositional savvy. When pressed about her occupation by a man she once knew, Maier didn’t describe herself as a nanny. She said, “I am sort of a spy.” All the best street photographers are.

Maier’s covert work might have languished in obscurity if not for the chance acquisition, in 2007, of a cache of negatives, prints, contact sheets, and unprocessed rolls of film, all seized from a storage locker because she fell behind on the rent. When John Maloof, a Chicago real-estate agent, bought the material, everything about Maier’s identity was a mystery except for her name. It was only when he ran across her death notice, two years later, that her story began to unfold. (His wonderful documentary on the subject, “Finding Vivian Maier,” was nominated for an Academy Award in 2015.) Maier shot in both color and black-and-white; perhaps to establish her credibility as a “serious” artist, the first of her pictures to be widely disseminated were the latter. Now that Maier has earned her place alongside Arbus, Robert Frank, Lee Friedlander, Lisette Model, Garry Winogrand, and other giants of the American street, a new book, “Vivian Maier: The Color Work,” and a related exhibition at Howard Greenberg Gallery (opening on November 14th) consider her eye for the vivid.