Michael Ong has never seen "Rambo III," but from a photograph of actor Sylvester Stallone, he carefully paints a sneering Rambo many times life-size, sweat-soaked muscles and all.

Ong is a "Billboard Michelangelo," one of a dwindling group of Singapore artists who painstakingly create huge film billboards that often are more intriguing than the films they advertise."The most difficult part is the faces," said Ong, surrounded by partial billboards depicting several Hollywood productions. "Not only must the stars be immediately recognizable, but their expressions riveting."

Slick posters and photos adorning Western theaters have never caught on among Asian film fans. They are far more impressed with towering billboards, a potpourri of glamor, romance and adventure created by painters banking on imagination and speed.

Ong, 40, is one. He and two assistants spent only a week on a panel for "Die Hard," so huge it wrapped around the theater building. "Rambo III" stood 40 feet by 15 feet as movie bait for the pedestrians passing by.

"These billboards are tremendous crowd draws," said C.Y. Chen, in charge of marketing for Shaw Brothers, a major movie distributor. "In comparison, prints and photographs look dull."

"The 40-footers are particularly appealing," Chen said. "It's hard to wander by without going in."

Artists like Ong, hired by the distributors, usually work only from movie stills. Often, as with "Die Hard," the pictures are in black and white. The same photos must also inspire a selection of small billboards, all different.

Since theaters want billboards in place long before the films open, Ong is used to weeks without a day off, tackling several at a time of varying sizes.

Determined to produce the most realistic facial color possible, Ong went to Rome and submerged himself in the museums, hopeful of picking up hints from the works of the masters.

"Obviously we're not in their league," Ong said, "but the trip helped."

Ong starts by tracing the outlines of the photograph on clear plastic, then projects the enlarged image onto canvas and traces again with charcoal.

Transforming all that space into a humorous, romantic, violent, gory, frightening or adventurous billboard is what makes the effort fun, said Ong, who works in shorts in a sweltering studio with paint streaking his arms.

"This is not a technique taught in school" he said. He began painting billboards at 18 because "I liked to paint and I loved the movies."

After a long apprenticeship with a veteran billboard painter, Ong joined a movie distributor and then started his own business, Golden Light Advertising.

"At first all I was allowed to paint was background," Ong recalled. "When I showed I could handle that, I was given more detailed scenes and the bodies, hair and clothing of the actors and actresses. Faces came last."

Apart from giant rooftop billboards, painters say smaller billboards 6 feet square often require greater skill because of the intricacy of the scenario.

Chen approves preliminary sketches before the artists proceed with the final product in emulsion paint.

"Likeness is essential," Chen said. "The concept must be compelling, enticing people enough so they'll want to see the film."

Geraldine Lee, spokeswoman for another distributor, said the billboards "dress up the cinema unlike any other promotional technique."

Like Ong, Chen fears the craft is dying, with the younger generation impatient with long apprenticeships and low pay compared with more lucrative fields such as advertising for their artistic inclinations.

There is no public recognition either. Billboard artists don't sign their works.

"There aren't many people creating these billboards, and it's a shame," Chen said. "I'm afraid extravaganzas will be part of our past, and there will be prints hanging instead."