"The world is in color," reasons William Eggleston. From his home in Tennessee, Eggleston, one of the pioneers of color art photography in the United States, recalls the days when the medium was still emerging as an accepted art form.

"I would show people what I was working on, and I don't think they knew how to react," he says. "They wouldn't have much of a response, and I couldn't tell whether they liked it or not."

In a booming yet jovial Southern drawl, he speaks slowly, as if mulling over every word, and recounts how, at the time he started working in the medium, color photography was only seen in advertisements and fashion spreads.

"If I didn't get a really positive response from people … it was probably because they were not used to seeing color in art photography pictures," he recounts.

Joel Meyerowitz, New York City, 1974, chromogenic print.

With vivid oil paintings and robust sculptures to compete with, photography as a medium has always had a tough haul in the art world. Daguerreotypes and other processes were dismissed as little more than a portraiture tool upon their 19th century introduction. Flash-forward a century and a half: Although it still wages battles against the uber-purists who view it as "easy art" that can be made just by hitting the shutter release, without the skill and discipline of other mediums, black-and-white photography on the whole has found a comfortable seat in the annals of art, with expressionistic color photography also widely accepted.

In between, however, there was a transitional period where black-and-white was cautiously embraced by collectors, but color work was almost entirely snubbed. In a sense, it suffered from the same fate black-and-white did a century before; it was regarded as cheap and shallow, either a tool for advertisers or the snapshot product of amateurs. "Mavericks of Color Photography," an exhibit running at the Philadelphia Museum of Art through November, takes a look at this curious time. Man Ray and other Dadaist photographers spent the 1920s and 1930s showing that photography needn't necessarily translate to cookie-cutter portraiture, while 1940s shooters like Robert Capa and Henri Cartier-Bresson set the era's standard for the painstakingly printed black-and-white image. By the mid-1950s, the art world saw this and gave its stamp of approval. But it wasn't quite ready for the work of someone like Eliot Porter or Eggleston.

Eggleston's work ranges from pictorials of life in his native South to rich abstracts, but both ends of the spectrum involve interplay between the colors within the frame. A hotel room in Greenwood, Miss., is painted a deep cherry red, and the lens crops up against the intersection of the two walls and the ceiling, presenting the single-tone room broken up by the black lines of electrical cable strung overhead and the hot white light bulb hung from it.

Another picture, taken at a farm between Minter City and Glendora, Miss., shows a cornfield on a sunny day. A black girl in a green dress and a blue bonnet is standing at the roadside, her hat blending into the blue of the sky and the dress blending into the green of the corn.

One can picture the lively young shooter, thrilled at last to have a range of hues in his palette and the ability to photograph these scenes.

"That was a Sunday and she was probably dressed for church," Eggleston says, recounting the latter picture's capture. "But I saw her walking down the road carrying a bag to get water from the well. These were familiar sites I grew up seeing — that place was right where you turned off the main road — and I happened to notice the way her clothes matched the scene. I immediately took the picture and went about my way."

Joining Eggleston's work in the PMA exhibition is the nature photography of Elliot Porter. While he has been described by some as the Ansel Adams of color photography, Porter's work actually approaches the same subject matter in the opposite way. Adams went for big, broad, beautiful — some might say bland — landscapes and vistas, whereas Porter's photography heads in for close crops, finding beauty in the detail of flowers on a glacial rock or the sweeping lines and curves in desert sand.

Also included is Joel Meyerowitz's New York and Paris street photography, which carries traces of the greyscale work of Louis Faurer and Diane Arbus; and William Christenberry's rural architectural studies — rusted-out, decaying gas stations and dilapidated brick buildings in Alabama — which seem to echo some of Eggleston's own subject matter.

The two actually met when Christenberry moved to Tennessee to teach art at Memphis State University. Eggleston remembers Christenberry as a painter and sculptor who had just begun to dabble in color photography, and says the two remain friends to this day.

"Neither of us made any effort at all to copy off of each other or model our work off each other," Eggleston says. "Although you can't help but be influenced by someone when you're working so closely."

While Eggleston says New York galleries didn't pick up on color photography for another 15 years (he had a solo show at the Museum of Modern Art in 1976), he stresses that the work of these shooters was brewing the entire time.

But color photography ultimately overcame its youthful hurdles — today's mavericks seem to be photographers shooting in the digital realm.

As someone who knows what it's like to feel excluded from the art world, Eggleston is very open to digital art. Earlier this summer, he judged an open-call photography exhibition in Japan where "99.9 percent" was color, and much of the color was from digital cameras.

He was floored by the work, but is a bit more cautious in incorporating it into his own shooting.

"You have this security with film, you know your pictures are going to be there," he says. "I've just barely come to grips with starting to trust digital. But I've just acquired some digital equipment as well. Ask me what I think of it in about a year."

"Mavericks of Color: Photographs from the Collection," through Nov. 27, Philadelphia Museum of Art, 26th and The Parkway, 215-763-8100.