He doesn’t need batteries or memory cards or even film for his pictures. Mostly he just needs time, patience and lots of elbow grease. And as he labors, moving methodically from beneath the hood of his wooden box camera to a portable field darkroom, bearing wet iron plates that he has painstakingly prepared, he thinks of himself not as simply making pictures but also as taking part in the world of the cowboys who are the subjects of his otherworldly tintype portraits.

“The tendency of cowboys is to think of photographers as very demanding, high-maintenance people,” Mr. Kendrick said. “And in the end I think they really respect the fact that I have to work for these pictures. They respect any kind of honest hard work.”

Mr. Kendrick belongs to a growing group of commercial and art photographers — including gallery stars like Sally Mann and Chuck Close — who have retreated in recent years from the ease and exactitude of the digital age and taken up the difficult, ethereal techniques of early photography, including the ambrotype (in which a unique image is created on a glass plate), daguerreotype (on polished silver) and tintype (usually on tin-plated iron ).

The latest result of Mr. Kendrick’s twin obsessions — with tintypes and the bow-legged anachronisms who continue to make their living on horseback — is “Still: Cowboys at the Start of the Twenty-First Century,” a new collection of 148 tintype portraits published by the University of Texas Press.

The pictures — made by exposing and developing the metal plates after they have been coated with a light-sensitive solution of silver nitrate — are a kind of ideal meeting of subject and style. Many of the cowboys pine to have been born in the 19th century. And the tintypes, with their sepia tones, blurred peripheries and ghostly aura, take the cowboys back to the era when such photographs were taken by traveling commercial photographers. Mr. Kendrick’s impulses may be more nostalgic and sociological than artistic, but the best of the pictures have a timeless power that evokes — oddly, given that Mr. Kendrick’s pictures are of cowboys — the portraits of North American Indians taken by Edward S. Curtis in the early 1900s.

For the new book, and an earlier one, “Revealing Character,” published in 2005, Mr. Kendrick estimates conservatively that he has covered more than 40,000 miles of often lonesome road in his pickup and visited more than 60 ranches, towing a trailer that he uses as a darkroom. (The most recent version of this mobile darkroom, specially made for him by a Mennonite company in Indiana, is as high-tech as his wooden cameras are primitive; it has an iPod docking station, climate control and stainless steel countertops.)

“When I’m doing tintypes, everything has to be driving, not flying — all the stuff for the developing is fairly flammable,” said Mr. Kendrick, who began to learn tintype techniques in 1999, after years of photographing cowboys with more conventional cameras and no toxic vats of potassium cyanide. “Fortunately for me I love driving,” he said, pausing before adding, “Thank God for satellite radio.”

Mr. Kendrick has long been drawn to cowboys as subjects, in part because he grew up around so many in Hereford, Tex., but also because he finds the endurance of their culture and mythology — more than a hundred years after the last great cattle drives — to be as fascinating as that of other groups he has photographed, like Sherpas in the Himalayas or the Tarahumara Indians of northern Mexico.

“Many cultures threatened by so-called progress can lose much in a matter of one or two generations,” he writes in the new book. “But cowboys — actual working cowboys, in all their manifestations — proudly and determinedly endure.”

As the era in which their livelihood was created recedes ever further and fascination with their stubborn embrace of it seems only to grow, cowboys also have to endure a lot of curiosity, from writers and filmmakers and photographers. And so Mr. Kendrick has had to work hard to overcome the impression that he is just another dilettante spectator.

“Some of us like the publicity, and some of us just get tired of it,” said Merlin Rupp, a 71-year-old lifelong range worker from Burns, Ore., who retired several years ago after a horse fell under him, badly breaking Mr. Rupp’s neck and, as he describes it with great understatement, “putting me to sleep for three weeks.”

But Mr. Rupp said he was proud of the stoical portrait Mr. Kendrick took of him, standing next to his wife, Faithe, the twirled ends of his long white mustache seeming to reach out toward her like tendrils. And Mr. Rupp said he believes that such portraits were an important record of modern-day cowboys at a time when cattle ranches are shrinking along with the number of working cowboys — or at least those he considers worthy of the name.

“There are fewer places to do this kind of work, but there are also fewer people who have the heart for it,” he said. “It’s a way of life that don’t pay a lot of money, and it’s hard on you. But it’s also stress free. You don’t have to drive 50 miles to work. You just get up out of your teepee and go to the cookhouse and then you go to work.”

Another cowboy, whom Mr. Kendrick has known for 20 years, David Ross of the Pitchfork Ranch in northwest Texas, spends winters alone in a range teepee on a wheat field, speaking to someone about once a month when his supplies are dropped off. “It’s good for a man to be alone,” Mr. Ross told Mr. Kendrick, whose photographs of him could be mistaken for those of a Rough-Rider-era Teddy Roosevelt. “It clears your mind.”

Over the years of riding, eating, bunking, branding and chewing tobacco with cowboys, Mr. Kendrick, 45, has become a fairly well-informed student of their regional idiosyncrasies and the ways in which they allow the modern world to seep into the 19th-century version that they try very hard to preserve around them.

Cowboys in northern and northwestern states like Oregon and Idaho and parts of Nevada and California tend to think of themselves not as cowboys but as buckaroos, a term that might sound as if it originated on the television show “Hee Haw” but is probably an Anglicization of the Spanish vaquero. Buckaroos are known, sometimes with a little derision, as the Beau Brummels of the saddle-office set, wearing antique-looking flat hats, leather brush cuffs, silver spurs, huge neckerchiefs they call wild rags and short chaps with long fringe, called chinks.

“These guys are very concerned with how their shadows look, whether they cut a good figure,” Mr. Kendrick said. “They don’t earn very much, but what they do earn they spend on their gear and they way they look.” (A starting cowboy salary can be less than a $1,000 a month.)

Moving further south on the cowboy map the term cowpuncher takes over, mostly in Texas, New Mexico and Oklahoma, where the work clothes are much more utilitarian and the brims of the hats arch skyward on the sides, a style that flat-hatted buckaroos call “taco hats.” (A good example can be seen in the well-known publicity picture of James Dean from “Giant,” sitting in profile with his boots up.)

Mr. Kendrick remembers a conversation with a Texas cowpuncher whose brim edges threatened to meet somewhere over the crown of his hat. “I said: ‘Tom, doesn’t that hat defeat the purpose of keeping the sun off of you? Doesn’t it shine right on your ears?’ ” The rancher told him that whatever the hat’s failings, its aerodynamics kept it from leaving his head in a high wind and it also sluiced the rain like a clean storm gutter.

The third major category of cowboy — those who call themselves just plain cowboys — tends to be found east of the Rockies, in Kansas, Nebraska, the Dakotas and Colorado and Wyoming, and its members usually find a middle ground between the fancy and the plain range looks. But Mr. Kendrick points out that it is much more common these days to see, for example, chink chaps in Texas or a taco hat far north, as cowboys migrate more and have better access to online shopping.

As the new book shows, though cowboying in the United States is still done mostly by white men, it is also more common to find cowgirls at work on ranches, not simply minding the books or cooking but on horseback, repairing fences and tracking lost calves. Jodi Miner, who runs the Snowline Ranch in Montana with her husband, Wes, told Mr. Kendrick in a series of interviews he has recorded and transcribed that she tries to live according to the dictum of working like a man but knowing when to be a lady.

“I’m proud to be a cowboy,” she said. “Or a cowgirl, however you want to word it.”

Mr. Kendrick said that though there are few creature comforts when he is making his portraits, food is sometimes one of them. Among his chuck-wagon highlights, he counts a mincemeat pie made by a cook on the ORO Ranch in Arizona with a filling of cow’s tongue mixed with wild apples and berries. “You could have been in San Francisco or New York eating that in a really expensive restaurant,” he said. He also notes that there are many modern-day cowboys who like to live a little; one in British Columbia confessed to spending his recent winters windsurfing in Mexico.

But you get the impression that Mr. Kendrick, like most cowboys, is much happier when doing things the hard way. “Making these kinds of pictures, you don’t need the mental skills that you have to have a Ph.D. for,” he said. “It’s more like learning to be a carpenter. It’s work and it’s satisfying. What you get is unique, not mass-produced. You can’t repeat the process. So it’s the antithesis of digital.”

The feeling is one that Mr. Rupp knew well. He tells a story of herding a couple hundred cows on a ranch in Nevada and taking them to the crest of a trail, below which lay a seemingly endless prairie.

“I just sat on my horse and I looked down,” he told Mr. Kendrick. “Gosh, I was right in the middle of God’s flower garden. The wildflowers were just everywhere. The smell was so great. And I couldn’t help but say: ‘Thank you, Lord. Thank you, Lord, for just lettin’ me be out there.’ ”