ALEC SOTH has created a photographic career out of finding chemistry with strangers. On his frequent road trips through America, he’s drawn to loners and dreamers he spots from his car; sometimes he will do several pass-bys before striking up a conversation. Often that will lead to a portrait session with his large-format 8-by-10 view camera.

“It’s the bird flying around that swoops down and grabs the worm and then flies off,” said Mr. Soth, 39, who winced slightly at the ethical implications of that image. “But I have good intentions, and people very often enjoy that interaction. It’s almost like, finally, someone showed up and we can talk.”

Mr. Soth’s lush, painterly large-scale color prints, which reflect a striking intimacy and comfort between subject and photographer, first gained attention from the art world in 2004. A self-described “complete nobody” at the time, Mr. Soth, a Minnesota native, had made a self-printed book called “Sleeping by the Mississippi.” It included landscapes and portraits shot over five years on car trips alongside the river’s meandering path from Winona, Minn., to Baton Rouge, La., and drew on the American literary theme of the Mississippi as a metaphor for wandering and freedom.

After seeing a copy of the book, curators for the 2004 Whitney Biennial put him in the show; his image “Charles,” of a man in a flight suit standing on the roof of his house holding a model airplane in each hand, was used on the Biennial poster. An avalanche of coverage followed, touting him as one of the great discoveries of the show. This attention led to a more professional publication of the book by Steidl, along with representation by Gagosian Gallery and international assignments that precipitated his joining Magnum Photos.