Before the world premiere of his new film on Saturday night, Danny Boyle told a crowd of 650 here at the Telluride Film Festival not to expect a representational biopic. Rather, he said, his "Steve Jobs" is a meant to be a direct signal from inside the Apple co-founder's mind, “"with all of its wonders and all of its horrors."

In other words, reputation varnishing this is not.

As portrayed by Michael Fassbender, acting from a script written by Aaron Sorkin, Mr. Jobs is part genius and part monster, a man who seems to go out of his way to be cruel but who has a genius understanding of technology and marketing. Mr. Jobs's initial refusal to acknowledge that he fathered a daughter is a primary story line. "We don't have time to be polite," he snaps to a colleague at one point.

"Steve Jobs" co-stars Kate Winslet as an Apple executive who functions as his taskmaster and gatekeeper; Seth Rogen plays the Apple co-founder Steve Wozniak. The film ends in 1998, five years before Mr. Jobs was diagnosed with cancer and takes place almost entirely backstage at theaters where products are about to be unveiled.

The assembled festival pass holders responded warmly to the two-hour film. At one point about half way through the screening, after an argument scene with loads of tongue-twisting dialogue, an attendee shouted "Sorkin!"

Mr. Boyle, who was interviewed on stage before the screening, called "Steve Jobs" the most challenging film he has ever directed. "I tend to be a very visceral director and entertain through that with fast cutting, and what you're going to see tonight is very, very different," he said. "The challenge is try to create the space for the actors to act out these extraordinary scenes."

Mr. Sorkin's script ran roughly 200 pages, roughly double the standard length for a film, Mr. Boyle said.

"We were determined to shoot it in San Francisco because we thought by some osmosis you'll pick up something from the place in the world where this new digital age was born," he added. He said "finance people" suggested filming in Hungary to shave $5 million from the budget. "I'm very, very proud we didn't do that," he said.

"Steve Jobs" is set for release by Universal Pictures on October 9 after another premiere at the New York Film Festival.