This is a love story.

In a studio in Carmel, Calif., in 1934, a rising star of artistic photography stepped behind his camera and watched a former Portland schoolgirl disrobe. The images captured in that room were the opening shots of a partnership that would vault Edward Weston into the pantheon of American photographers. Eleven years later, Charis Wilson put her clothes back on, and darkness fell over her husband's lens.

It took more than half a century for a local filmmaker to turn the lights on Weston's muse again—and that man found himself surrounded by ATVs in Oregon's Honeyman State Park dunes, trying to find a location where he could shoot a naked woman rolling in the sand.

Charis Wilson is now 92 years old. Ian McCluskey is 34. But that age gap collapsed on a 2005 winter afternoon in Powell's Books, when McCluskey opened a book of Weston prints and was confronted by images of Wilson. The director, a veteran of Oregon Public Broadcasting projects, had browsed Weston's photos before, but this time he knew he was seeing something astonishing.

"You look at those photos, and you know that the camera's acting as a transmitter of a relationship," McCluskey says over beers. "It's not a one-way thing. And I see so many weekend nude photographers who will find this beautiful landscape—they try to do it right at sunset—and then they get this nude model they hired for the hour to drape herself over a log."

McCluskey knew Weston's shots were different. His search for that difference led him to Charis Wilson—and to Eloquent Nude: The Love and Legacy of Edward Weston and Charis Wilson, his documentary on the pair's collaboration that premieres March 8, at Portland Art Museum. The movie, made with the backing of NW Documentary Arts & Media and $117,000 in donations, is brilliant: part archival images, part historical reenactments filmed in the Oregon countryside, and all of it a meditation on love and loss.

The story starts in '34, when Wilson—a graduate of Portland's then all-girl Catlin Gabel School and at 19 already a veteran of San Francisco speakeasies—began modeling for (and sleeping with) the up-and-coming Weston, who was 48. She helped transform his photography. He went from shooting an anonymous body to shooting a woman—and the images of that woman, quietly posed or splayed in sand dunes, were iconic. Together they traveled the West Coast on a Guggenheim grant, occasionally joined by a kid named Ansel Adams. Weston took the photos; Wilson wrote the grant proposals and the essays and added something palpable to the shots. The rest of the story wrote itself. They married. They grew distant. She left. He soon stopped taking photos.

Everything else became the province of curators and academics, until McCluskey realized Wilson—who later remarried and raised children—was still living in Santa Cruz, Calif. "I was like, 'What a cool woman,'" he recalls. "It was maybe even a little selfish: I just want to meet this woman, and this camera is a less awkward reason than just showing up like a fan."

The interview complete in March 2005, McCluskey decided he needed more. So he gathered his own collaborators: people who would travel Oregon with him and re-create the journeys of Great Depression artists. Which is how he wound up in Honeyman State Park with model Christine Bersten—and realized that these days, dunes are used for more than photography.

"There's all these ATVs buzzing everywhere," he says. "And we're like, 'Oh, God—we've got a camera, and a nude model and a bunch of ATVs in the background.' Americana in your face: flags, hot dogs, thousands of ATVers."

The improvised nature of the doc is no accident. It's a reflection of the subject. "This is kind of like the DIYs of the '30s—Ansel Adams and Edward Weston grabbing their gear and heading up to Yosemite," McCluskey says. "If you just perfect the surface level, then you've lost the spirit of what they were doing, which was half making it up as they went along."

There's something wistful about a pack of Portland filmmakers drinking PBRs around a campfire as they try to recapture the adventures of two artists—the model a nonagenarian, the photographer long dead. That elegiac mood extends into every frame of McCluskey's documentary. It's the same feeling you get looking at an old photograph, seeing a moment forever lost and eternally present. That's the love story of Eloquent Nude.

"It's like, pure regret's not very interesting," McCluskey concludes. And pure love's not very interesting. But when you layer up love and regret, it becomes really interesting."

Eloquent Nude

screens at Whitsell Auditorium, 1219 SW Park Ave. 7 pm Thursday, March 8. $7. Screening followed by Q&A with McCluskey and others.