SAN FRANCISCO (AP) — Happily hunched over his iPad, Britain's most celebrated living artist David Hockney is pioneering in the art world again, turning his index finger into a paintbrush that he uses to swipe across a touch screen to create vibrant landscapes, colorful forests and richly layered scenes.

"It's a very new medium," said Hockney. So new, in fact, he wasn't sure what he was creating until he began printing his digital images a few years ago. "I was pretty amazed by them actually," he said, laughing. "I'm still amazed."

A new exhibit of Hockney's work, including about 150 iPad images, opened Saturday in the de Young Museum in Golden Gate Park, just a short trip for Silicon Valley techies who created both the hardware and software for this 21st-century reinvention of finger-painting.

The show is billed as the museum's largest ever, filling two floors of the de Young with a survey of works from 1999 to present, mostly landscapes and portraits in an array of mediums: watercolor, charcoal and even video. But on a recent preview day, it was the iPad pieces, especially the 12-foot high majestic views of Yosemite National Park that drew gasps.

Already captured by famed photographer Ansel Adams, and prominent painters such as Thomas Hill and Albert Bierstadt, Hockney's iPad images of Yosemite's rocks, rivers and trees are both comfortingly familiar and entirely new.

In one wide open vista, scrubby, bright green pines sparkle in sunlight, backed by Bridalveil Fall tumbling lightly down a cliff side; the distinct granite crest of Half Dome looms in the background. In another, a heavy mist obscures stands of giant sequoias.

"He has such command of space, atmosphere and light," said Fine Arts Museums director Colin Bailey.

Other iPad images are overlaid, so viewers can see them as they were drawn, an animated beginning-to-end chronological loop. He tackles faces and flowers, and everyday objects: a human foot, scissors, an electric plug.

Some of the iPad drawings are displayed on digital screens, others, like the Yosemite works, were printed on six large panels. Hockey's technical assistants used large inkjet prints reproduce the images he created on his IPad.

Exhibiting iPad images by a prominent artist in a significant museum gives the medium a boost, said art historians, helping digital artwork gain legitimacy in the notoriously snobby art world where computer tablet art shows are rare and prices typically lower than comparable watercolors or oils.

"I'm grateful he's doing this because it opens people's mind to the technology in a new way," said Long Island University Art Historian Maureen Nappi, although she described Hockney's iPad work as "gimmicky."

Writing about the historic shift of drawing from prehistoric cave painting to digital tablets in this month's MIT journal "Leonardo," Nappi said that while iPad work is still novel, the physicality of painting and drawing have gone on for millennia.

"These gestures are as old as humans are," she said in an interview. "Go back to cave paintings, they're using finger movements to articulate creative expressions."

Hockney, 76, started drawing on his iPhone with his thumb about five years ago, shooting his works via email to dozens of friends at a time.

"People from the village come up and tease me: 'We hear you've started drawing on your telephone.' And I tell them, 'Well, no, actually, it's just that occasionally I speak on my sketch pad,'" he said.

When the iPad was announced, Hockney said he had one shipped immediately to his home in London, where he splits his time with Los Angeles.

He creates his work with an app built by former Apple software engineer Steve Sprang of Mountain View, Calif., called Brushes, which along with dozens of other programs like Touch Sketch, SketchBook Mobile and Bamboo Paper are being snapped up by artists, illustrators and graphic designers.

Together, the artists are developing new finger and stylus techniques, with Hockney's vanguard work offering innovative approaches.

"David Hockney is one of the living masters of oil painting, a nearly-600-year-old technology, and thus is well positioned to have thought long and hard about the advantages of painting with a digital device like the iPad," said Binghamton University Art Historian Kevin Hatch in New York.

Hatch said a "digital turn" in the art world began about 25 years ago, as the Internet gained popularity, and he said today most artists have adapted to using a device in some way as they create art.

A similar shift happened almost 100 years ago with the dawn of photography, he said, when innovations such as the small photograph cards and the stereoscope captured the art world's imagination.

And Hatch said there are some drawbacks to the shift to tablet art.

"A certain almost magical quality of oil paint, a tactile, tangible substance, is lost when a painting becomes, at heart, a piece of code, a set of invisible 1's and 0's," he said.

Hockney, who created 78 of the almost 400 pieces in the de Young show this year, isn't giving up painting, or drawing, or video, or tablets, any time soon. When asked where he sees the world of art going, he shrugged his broad shoulders and paused.

"I don't know where it's going, really, who does?" he said. "But art will be there."

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  • In this photo taken Thursday, Oct. 24, 2013, people watch how a painting made by David Hockney using an iPad takes shape at an exhibit in San Francisco. A sweeping new exhibit of Hockney’s work, including about 150 iPad images, has opened in the deYoung Museum in Golden Gate Park, just a short trip for Silicon Valley techies who created both the hardware and software for this magnificent reinvention of fingerpainting. (AP Photo/Eric Risberg)

  • In this photo taken Thursday, Oct. 24, 2013, a man records how a painting made by David Hockney using an iPad takes shape at an exhibit in San Francisco. A sweeping new exhibit of Hockney’s work, including about 150 iPad images, has opened in the deYoung Museum in Golden Gate Park, just a short trip for Silicon Valley techies who created both the hardware and software for this magnificent reinvention of fingerpainting. (AP Photo/Eric Risberg)

  • In this photo taken Thursday, Oct. 24, 2013, a woman watches how a painting of Yosemite National Park, made by David Hockney using an iPad, takes shape at an exhibit in San Francisco. A sweeping new exhibit of Hockney’s work, including about 150 iPad images, has opened in the deYoung Museum in Golden Gate Park, just a short trip for Silicon Valley techies who created both the hardware and software for this magnificent reinvention of fingerpainting. (AP Photo/Eric Risberg)

  • David Hockney

    In this photo taken Thursday, Oct. 24, 2013, David Hockney gestures while explaining how he used an iPad to paint at an exhibit opening in San Francisco. A sweeping new exhibit of Hockney’s work, including about 150 iPad images, has opened in the deYoung Museum in Golden Gate Park, just a short trip for Silicon Valley techies who created both the hardware and software for this magnificent reinvention of fingerpainting. (AP Photo/Eric Risberg)

  • British artist David Hockney passes one of his paintings as he arrives for a news conference on the occasion of his exhibition "David Hockney - A Bigger Picture" at the Museum Ludwig in Cologne, Germany, Thursday, Oct. 25, 2012. The exhibition runs from Oct. 27, 2012 until Feb. 3, 2013. (AP Photo/dapd, Tim Schulz)

  • A general view of Vienna State Opera's new iron curtain painting by British painter David Hockney on November 20, 2012. (DIETER NAGL/AFP/Getty Images)

  • People walk past a painting entitled 'Portrait of Peter Langan,' (L) by David Hockney during a press call at Christie's auction house on December 10, 2012 in London, England. The painting makes up part of the 'Rule Britannia' modern British art evening sale and is expected to fetch between GBP 100,000 and GBP 150,000 when it goes on sale on December 12, 2012. The sale includes pieces from restauranteur and art collector Peter Langan, whose Langan's 'Brasserie' and 'Odin's' will sell some of their collection which includes works by David Hockney. (Photo by Dan Kitwood/Getty Images)

  • Gallery staff pose for a picture as they hang a painting by British artist David Hockney entitled 'Mr and Mrs Clark and Percy' during a press preview at the Tate Britain in London on May 13, 2013. The preview was held ahead of the opening of an exhibition showcasing 500 years of British Art. (ANDREW COWIE/AFP/Getty Images)

  • Sotheby's employees pose with a piece of work entitled 'Wilshire Boulevard' by David Hockney at Sotheby's auction house on September 3, 2013 in London, England. The piece makes up part of 'The New Situation' exhibition, comprising of 1960's British Art including paintings by David Hockney and Bridget Riley. The exhibition runs at the auction house until September 11. (Photo by Dan Kitwood/Getty Images)

  • A Christie's employee poses beside an early piece of work by David Hockney during the 'When Britain went Pop!' exhibition at Christie's auction house on October 8, 2013 in London, England. The exhibition claims to be 'the first ever Comprehensive exhibition of British Pop Art to be held in London' and includes work by artists including David Hockney, Peter Blake, Richard Hamilton and Allen Jones and opens to the public until November 23. (Photo by Dan Kitwood/Getty Images)

  • A painting 'Double East Yorkshire' by David Hockney is seen on display as workers prepare the gallery at Sotheby's auction house in London, Friday, June 14, 2013. The painting is to be auctioned in Contemporary Art sale on June 26 with an estimated price of 2 to 3 million pounds (US$ 3.13 to 4.69 million or 2.35 to 3.52 million euro). (AP Photo/Sang Tan)

  • A woman walks past artwork by David Hockney created when he was an RCA student in the early sixties in the 'Perfect Place to Grow' exhibition at The Royal College of Art in celebration of their 175th anniversary on November 15, 2012 in London, England. The Royal College of Art's major exhibition, 'The Perfect Place to Grow', features over 350 works of art and design by RCA graduates and staff including: Henry Moore, Tracey Emin and David Hockney. The RCA is the world’s oldest art and design university in continuous operation and it currently educates 1,200 postgraduate students from 55 different countries. (Photo by Oli Scarff/Getty Images)