Diane Arbus was American photography’s bravest detective. Born in 1923 and raised in leafy privilege, the young Arbus spurned the path of bourgeois domesticity to patrol the outskirts and no-go areas of the demimonde, armed with only a 35-mm Nikon and a fierce supply of inquisitive nerve. She haunted flea circuses, carnival sideshows, and strip clubs, and recorded life on the fly on New York City streets. Like so many photographers in the heyday of Henri Cartier-Bresson, Arbus was in pursuit of the “decisive moment,” the chance epiphany. It was when she upgraded from the Nikon to the medium-format Rolleiflex, with its bulkier body, larger negative, and square frame, that she found her true eye, her visual voice. What was revelatory at the time and remains controversial to this day was that Arbus’s subjects were people who had been marginalized, stigmatized, and ostracized by polite society and mainstream culture. The classical poise and becalmed clarity of the images, their eerie hold on the viewer—that’s why they’ve endured. This exhibition, presented jointly by David Zwirner and Fraenkel Gallery, commemorates the 50th anniversary of MoMA’s pivotal 1972 Diane Arbus retrospective. All 113 photographs are included. —James Wolcott