Do these faces look familiar?

It was like seeing double, but more so. It was like “This Is Your Life,” but without voice-overs. It was an echo tunnel, made visible. It was the opening of the David Hockney portraiture show at the Los Angeles County Museum of Art.

For an insiders’ viewing Tuesday and then a press preview and luncheon the next day, the museum invited 20 of Hockney’s subjects, who lingered and mingled with each other and their two-dimensional selves -- many in the same outfits Hockney had painted them in -- while the artist held forth.

The result was a strange visual resonance -- but perhaps less odd for the man of the hour, who not only knows most of these people well, but has spent five decades looking back and forth between model and canvas. Since his first visit to L.A. in 1964, the Yorkshire-born artist has spent most of his time in California. As he explained for the gathered media, Hockney prefers to paint his family, friends and business associates “because I can be a little bit more sure what they look like.”

On the whole, he seemed a casual, philosophical, go-with-the-flow sort of guy. Which, his assembled subjects agreed, is entirely wrong.

Once the brush is in hand and the sitter is in place, they said, there’s not much kidding around, just sustained quiet and, for those who find themselves standing in uncomfortable shoes, hours of regret.

“To see David, and then to see him at work -- it’s very different,” said photographer Jim McHugh, who sat for a 2005 portrait with his daughter Chloe. “His intensity is like a laser.... He sees everything. And a tiny flick of his brush will entirely change the complexion of a portrait.... The portrait he did of us was so accurate, psychologically.”

Chloe McHugh, 16, wearing the same green 3-inch heels she wore for the portrait, recalled the sessions with a grimace: four days, six hours per day. “I didn’t realize that I’d be standing the entire time.... It was painful, but worth it.”

Leon Banks, a Los Angeles pediatrician who wore the same black Gucci loafers as in his 2005 portrait, said it was painless for him -- two sessions in Hockney’s studio off Mulholland Drive, about two hours each. But by now, Banks knows what to expect. Since the two met in the late 1960s, Hockney has drawn or painted Banks several times.

“He waits for you to find a position that you’re comfortable in. And then you’re obliged to keep it,” said Banks. “He’s very serious, very devoted.”

Does he talk?

“Not very much,” said Banks. “And you can’t talk, either. You meditate.”

The artist, who will be 69 next month, wore a white cap, blue shirt and gray jacket. He said he sympathized with the plight of the sitter, having once spent 120 hours posing for a portrait by Lucien Freud. But he also said he likes to remind his sitters to “remember Betty Lisa.”

Betty Lisa, he explained, agreed to sit for a portrait, then discovered she couldn’t make the appointment. So at the last minute she sent her sister, Mona.

When the giggles and groans died down, Hockney also told the assembled crowd that he is “going quite seriously deaf” and that he abandoned reading “The Da Vinci Code” after a single page. In response to a question, he said that if there’s a message embedded in the portraiture show, it’s something along the lines of “ ‘love life,’ I suppose.”

Yet for further proof of the artist’s tenacity in studio circumstances, consider Sidney Felsen and Joni Moisant Weyl. Felsen and Weyl, art-business veterans who have worked with Hockney on print publishing and sales for decades, sat for a Hockney double portrait early last year, then returned from a big trip to find he’d shelved it.

“It looked finished, but there were some things about it that David was not comfortable with,” said Weyl. So they started over, this time with Sidney wearing a broad-brimmed white hat, a summer suit and a bow tie, and the result of that sitting hangs now in LACMA.

Not far from Felsen and Weyl -- and the Felsen and Weyl canvas -- stood Charlie Falco, a professor of optical sciences at the University of Arizona who has collaborated with Hockney in his investigations of lost techniques of the Old Masters.

Falco wore the same blue shirt, blue tie and dark suit seen in his portrait. And he recalled the sitting with a scientist’s exactitude: It was a Monday and Wednesday in March 2005.

“For the first hour and a half, he’d look at me for two seconds, then at the painting for two seconds. Two seconds, two seconds. For an hour and a half. The intensity,” Falco said. After that, the intervals of looking and painting came to last longer and longer.

For Peter Goulds, director of the LA Louver Gallery and Hockney’s West Coast dealer for 27 years, the picture came out of a single session in the artist’s studio, 10:15 to 4:45 on a Sunday, with an hour and 15 minutes off for lunch. Hockney had instructed Goulds to dress up and made him stand up.

In the painting, Goulds presses one finger to his cheek as if thoughtfully assessing a painting -- and in fact, Goulds recalled, he got through the hours by focusing on another portrait that stood behind Hockney in the cluttered studio.

Yet the finished image “was a shock to me,” Goulds said. After years of close acquaintance with Hockney and his pictures, he doesn’t doubt the truthfulness of the image, but “it’s not how I see myself. It’s a level of intensity I’m not aware of in myself.”

The show, which runs Sunday through Sept. 4, includes about 120 portraits produced over five decades in oil, watercolor, ink and other techniques. It was organized by the National Portrait Gallery in London and the Museum of Fine Arts, Boston.

Introducing it to the press, the artist fielded questions on the light in L.A. (it’s good) and the lessons one learns while painting portraits (probably the same lessons that one would learn doing something else) and denied possession of any secrets necessary to the making of great art.

“How you make a memorable picture, I have not a clue,” he said. “And neither does anybody else. Or there would be a lot more of them.”