“Peter Hujar’s Day,” which premiered at this year’s Sundance, has sold to Sideshow and Janus Films. It’s one of the few projects to land a buyer out of the festival so far.

Written and directed by Ira Sachs, “Peter Hujar’s Day” is set over a 24-hour period in December 1974 and centers on one conversation between photographer Peter Hujar (Ben Whishaw) and his close friend, writer Linda Rosenkrantz (Rebecca Hall), who recorded their talk for an art project. Hujar, who died of AIDS in 1987, only became celebrated as an artist after his death.

The film debuted in Park City to positive reviews, with Variety’s Owen Gleiberman calling it a “magical 1974 time capsule of a movie.” In his review, he wrote that “in its tiny-scaled staged-documentary way, ‘Peter Hujar’s Day’ is exquisitely done and arresting to watch.”

“Peter Hujar’s Day” will screen at the Berlin Film Festival before Sideshow...