From a New York Times online article:
Rigorously unsentimental in his attitude to the world around him, Mr. Frank deviated from form in 1950, taking what was arguably his most romantic picture. He had his reasons. He was in love. The year before he had met artist Mary Lockspeiser, who became his first wife. In “Tulip/Paris,” he photographed a young man who is holding behind his back a tulip — presumably intended for the woman standing in the background. An old man, at the other end of life’s arc, approaches the viewer. It is a classic romantic Paris street photograph.
Robert Frank kicked documentary photography into the present with a loud clang. In place of the detached formalism of Walker Evans and the poetic lyricism of Henri Cartier-Bresson and Andre Kertesz, he brought a moody, cool intensity that stamped his pictures with a readily identifiable hallmark. Using a 35-millimeter Leica, he could compose images as elegantly framed as if he’d set up a tripod, or as blurry and off-center as an amateur snapshot. He took whatever means he needed to express a vision that was alternately empathetic and obstreperous, as contradictory as the man himself.