NEW YORK -- Andy Warhol once predicted 15 minutes of fame for everyone.

But 25 years after his death, the pop artist's reputation and impact on the contemporary art world show no signs of fading. His iconic images of everyday consumer objects and celebrities consistently command high prices and draw enthusiastic crowds to museum and gallery shows.

But before he catapulted onto the world stage, the young artist was already producing some of his most iconic pieces. In a new exhibition, Warhol is captured in photographs at the very cusp of the pop art movement.

"Before They Were Famous: Behind the Lens of William John Kennedy," at the Site/109 gallery in lower Manhattan, features rare shots of Warhol and artist Robert Indiana posing together with what were soon to become their most celebrated works – Warhol's "Marilyn" and Indiana's "LOVE" logo.

Kennedy, a freelance photographer when the photos were taken, had nearly forgotten about them and only rediscovered the images several years ago in a "beat-up cardboard box" while sorting through his archive, he said.

He took them when Warhol "was a known entity but had not yet exploded on the scene," said Eric Shiner, director of the Warhol Museum, located in Warhol's hometown of Pittsburgh. "They capture Andy both in production mode and also having fun mode."

The 82-year-old photographer, who lives in Miami Beach, Fla., said he set out to record "the rising stars of the new movement in pop art." He sensed immediately that Warhol would become "a giant in the industry" but said he "was amazed to meet this very withdrawn and taciturn man."

Among his favorite photographs is one of the pop icon working at his Manhattan studio, The Factory.

"Piled up in the corner were 50-75 sheets of acetate. Andy said `Those are proofs of my work,'" Kennedy recalled. As he unrolled one, "there's this huge face of Marilyn Monroe – a transparent proof of his silkscreens."

He had Warhol hold it up in front of him, creating a portrait within a portrait.

In another image, the photographer posed Warhol with one of his early flower paintings standing in a field of black-eyed Susans, located in a most unlikely spot – an industrial section of the Flushing neighborhood in New York City's Queens borough.

These and about 50 other silver gelatin prints of Warhol and some 30 of Indiana capture the artists in their studios, relaxing, editing, painting and chatting on the phone. The works – presented by the Miami-based publishing house Kiwi Arts Group – are shown alongside some of the artists' originals works.

Kennedy shot hundreds of images of the artists; 100 will be placed in the permanent collection of the Warhol Museum.

The exhibition, which runs through May 29, also includes a 40-minute documentary film featuring people still living who were involved with Warhol, including such Warhol superstars as Ultra Violet and Taylor Mead.

"What's great is all these people are in their 80s. We were able to capture them in this juncture about a period that was almost lost in the early 1960s at such a monumental, pivotal point in the pop art movement," said Kiwi Arts founder Mike Huter.

Warhol, who used every available medium to create his brand of imagery, died in 1987 at the age of 58. His output was prolific.

"If you amass all the sales of Warhols, he is by far the most sold ... in the art world" today, said Alex Rotter, Sotheby's pop art expert, adding that Warhol began attracting museums and collectors in a big way in the 1980s.

The current auction record for a Warhol is $71.7 million. Privately, one of his works has sold for more than $100 million.

The show at the Site/109 gallery is just one of many current or planned Warhol exhibitions around the world.

A major Warhol retrospective is now on a five-city tour of Asia. After it concludes in Tokyo in 2014, it may travel to New York, Mexico City and possibly Istanbul, said Shiner.

During New York's Frieze Art Fair next month, the Warhol Museum will show some 20 Warhol Polaroids alongside those by Jeremy Kost, a young New York artist who works under the rubric of the great pop artist. And Affirmation Art, a nonprofit art space in Manhattan, is showing 50 Warhol photographs, eight of which have never been seen outside the Warhol Museum.

But the showstopper will be a major exhibition at the Metropolitan Museum of Art titled "Regarding Warhol: 50 Artists, 50 Years." Scheduled to open in September and travel to Pittsburgh in 2013, "it will be a blockbuster exhibition showing how deeply entrenched Warhol is in contemporary art," Shiner said.