Here's the thing about filming a guy who's climbing a 3,000-foot rock formation without safety gear: You don't want to get in his way.

That was the main goal of married co-directors Jimmy Chin and Elizabeth Chai Vasarhelyi, who just won an Oscar for their National Geographic documentary "Free Solo."

The filmmakers spent a "harrowing three years," as Vasarhelyi described it at Los Angeles Film Festival, shooting their film about climber Alex Honnold's unbelievable solo summit of Yosemite's El Capitan wall without ropes. The movie drew good crowds in its limited release (averaging more than $75,000 per screen, the year's best to date) and is now available on to stream on Amazon, iTunes, YouTube and Google Play. Nat Geo's channel is also airing the movie on Sunday, March 3.

So how did filmmakers manage to get dramatic 4K footage of Honnold's ascent, complete with sweeping shots of Yosemite and close-up views of his fingertips, all without distracting arguably the best climber of all time? Chin explained it to USA TODAY.

They never asked Alex when he'd climb.

Chin, who has climbed and shot video with Honnold, 33, for several years, would never ask when it was time for the El Capitan climb. He didn't want to worry Honnold. "It had to come from Alex when he was going to do it," Chin says. "We spent a lot of effort (trying) to shield him from the pressure of production."

That meant that the filmmakers spent years preparing for the free-solo summit – a climb without rope or partners – whenever it happened, if it happened. And without telling Honnold about what they would do when it happened.

At one point, they even started filming what they thought would be the climb before Honnold quit. The team would return months later, when Honnold felt better prepared.

The cameramen were professional climbers.

"Our shot list and our positioning and our rigging and logistics were totally surgical," says Chin, who was careful not to make noise while shooting to avoid distracting Honnold. He and four other shooters moved along different parts of the wall, with their gear, so they could get a variety of angles for Honnold's ascent.

"How do you shoot it so you’re not in anybody’s shot? That took some time, but we had two years to figure it out," says Chin, who worked with a 15-person crew the day of the climb and had more than 30 days of practice shooting on El Capitan.

Videographers looked like window washers.

Chin says he looked "like a dangling window washer" while shooting the nearly four-hour climb.

"I was hanging off of a rope with a bunch of gear dangling off of (me) and a bunch of ropes clipped off in coils so the rope isn't in the frame," he says.

Chin and his fellow cinematographer-climbers weren't responsible only for getting good shots but also for doing work that's typically handled by several crew members.

"We don't have a rigger or focus puller and are carrying all of the batteries, food, water, memory cards for the day," Chin says. "The only people who could've done the shoot were the people on this team."

Honnold went only when he felt ready.

In "Free Solo," Honnold emphasized that he cared much more about free-soloing El Capitan as a personal goal than he did about filming it for the world to see. "Having people around requires a high level of preparation. I need to feel (confident)," he said.

Indeed, Honnold felt so good on the day of the climb that he smiled for the cameras.