In his street photography, though, there is a telling difference from the pictures of Mr. Winogrand or Robert Frank. The American photographers depicted crowds of atomized individuals. When Singh looked about him in India, he found intimate moments of human interaction — a boy carrying a baby, a barber cutting a client’s hair — within the wider flux of teeming humanity. “What was amazing in the last decade of Raghubir’s life was the modern vision he developed, with such a deep understanding of India, which was in his blood,” said Ketaki Sheth, one of the younger Indian photographers whom Singh mentored.

Sometimes, Singh’s photographs function as commentary. A picture taken outside the former Victoria Terminus in Mumbai (then Bombay) shows men in jeans and chinos hurrying to work, while in the foreground a vendor is holding a mosquito net that frames a view of its imposing stone lion. “To me, it is a complete sentence — all the men are in Western dress and they think they are catching the British lion in a mosquito net,” said Ilan Averbuch, a sculptor who was a close friend of Singh’s. A photograph of a wrecked truck and an oblivious cowherd recalls the Bruegel painting of the fall of Icarus, about which W. H. Auden wrote a famous poem; but unlike Bruegel’s disaster, which unfolds as a speck in the sky, Singh’s downed truck takes up more than a third of the frame, pushing up to the picture plane and dwarfing the man and his cattle. In India, catastrophe is always in your face, but it can be — must be — sidestepped.

In his final completed project, on the boxy Ambassador car that was ubiquitous during the period he traveled in India, the doors, windows and rearview mirrors of the vehicles divide and complicate the image. “His work became more abstract,” said Gwen Darien, an art historian and patient-rights advocate who was his partner during the last year of his life. At the time of his death, he was about to travel to Chicago, where his first American museum retrospective had just opened at the Art Institute of Chicago. “I think he was at a significant turning point,” Ms. Darien said. “It was a new place of his engagement with other photographers and the public. It is so heartbreaking that that was the moment when he died.”

One of his last, unfinished projects was a series of what we now call selfies in different settings. Mr. Roma said he thought these self-portraits differ in motivation from the well-known self-portraits of Mr. Friedlander (who is Mr. Roma’s father-in-law). “Lee is projecting himself on the landscape,” he said. “Raghubir was almost doing the opposite, projecting the landscape onto himself.” Singh was contemplating the impressions left on him by the many places he happened to visit, and the singular place from which he hailed. “He always claimed that he was shaped by Rajasthan,” said Akeel Bilgrami, a professor of philosophy at Columbia University. A 1998 self-portrait in Rajasthan illustrates that. Bespectacled and quizzical, Singh fills much of the frame, but he is out of focus. The courtyard and servant in the traditional house behind him are rendered sharp and clear.