George Allan, a Kula, Maui, painter, once dropped his glass palette and had to dig the little bits of paint out from under the shattered pieces. "But I still painted, and it's one of the best paintings I've ever done," he recalled.

Every outdoor painter has stories of friendships formed over the palette, works sold right off the easel, and learning from others during plein-air "paint outs" — group art-making trips.

But the primary reason for working outdoors is the same for today's plein-air painters as it was for the European artists who founded the movement: the light, and the moving-target challenge of capturing the scene before the light changes.

"It's extreme painting," said Jan Bushart, a Kihei, Maui, painter and organizer of the new Plein Air Painters of Hawai'i. "We're challenged to concentrate completely on our surroundings, we become immersed in the scene and in quickly putting that on canvas — a scene that can change with the movement of the sun, the weather, the tide coming in."

Plein-air painting is undergoing a renaissance, said Sprecklesville, Maui, artist Julie Houck, regional editor for the five-month-old national Plein Air magazine.

Allan, a respected art teacher and the first honorary member of Plein Air Painters of Hawai'i, considers plein-air "paint outs" a valuable teaching tool. "Paint outs," which often include a mix of beginners and professionals, allow participants to absorb technical tips and tricks. "You see people do things you might never have thought of. I think that's why the plein-air movement has gotten so strong; it's a way of learning without actually taking a class," said Bushart.

And in plein air, the artist spends considerable time looking closely, first choosing a scene to paint, then observing still more closely that piece of nature they have chosen. "You develop that vision, that ability to really see, and it's an accessory to life — everyone should do it.

You do yourself a lot of good by training yourself to see; that's what art is about," Allan said.

Seven years ago, Allan took a workshop class outdoors to paint. A loose-knit group grew from the workshop, members call themselves the Wednesday Painters and visit a different Maui location each week.

Plein-air painters are their own form of advertising and a sort of diplomatic corps for art. Everyone stops when they see a painter at work, most smile, many comment (Bushart says she could write a book about the things people say).

Allan takes this opportunity to give a mini-lesson. He doesn't resent the intrusions: "You understand what you're doing, your own process, much better if you have to explain it to someone else."

The roots of plein-air painting date to late 17th- and early 18th-century painters who went outside to do studies for their studio paintings. Plein-air work famously flowered with the French Impressionists in the 19th century. "They started painting outside as an actual genre, not just a means to an end. ... They started painting ordinary people doing real things; they got away from the aristocratic, allegorical and religious subject matter and came out into the open air," Houck explained.

The exact definition of plein-air painting is the subject of some esoteric debate: Purists say the work must be made, start-to-finish, outdoors. Others still consider a work plein air if it is given a few finishing touches indoors after being largely painted on location.

"The most important thing isif the piece was derived from nature, if it was given birth outside, and if the artist spent the time in front of the easel outside," said Houck. "What really counts is, is it a good painting?"

Plein Air Painters of Hawai'i will offer learning opportunities, competitions, interaction with established artists and member profiles on the Web site www.pleinairpaintersofhawaii.com.

The organization is meant to supplement, not compete with, the many plein-air groups in the Islands. The Association of Hawaii Artists has formed a new plein-air arm (www.geocities.com/association_hawaiiartists).

A key component is the signature member category: established artists who offer guidance, jury shows and lend stature to the group.

Artists must apply for signature membership and 10 will be selected by a juror, John Cosby. Cosby is a Paso Robles, Calif., artist who began painting as a child, setting up his easel next to his grandmother's. He helped found the Laguna Plein Air Painters Association (www.lpapa.org).