When the Swiss photographers Mathias Braschler and Monika Fischer took a six-month road trip across the United States for their portrait series “About Americans,” it was a journey through a foreign land. Sort of.

They spoke the language. They had comfortable motels. They could eat hamburgers.

That all changed when the pair, who had never been to China, decided to undertake an ambitious road trip there, hoping to visit every one of the country’s 33 provinces and regions.

Months later, as they were being arrested while making a portrait in Hubei Province, they knew a lot more about China. And themselves, too. The project, Mr. Braschler acknowledged, “was a little bit ambitious.” During their first month, which they spent in Beijing, he started keeping a diary. “After a couple of weeks I wrote in that diary, ‘I wish we never had this idea,’ ” he said. “We knew it was a big mountain, but once we were in China, we just realized how big that mountain was.”

The resulting series, “China,” is a historical document of a country as its villages turn into cities; its cities into megacities. Shot before the 2008 Beijing Olympics, the portraits present a diverse nation through its people: yak farmers, gynecologists, television personalities, village chiefs, singing gondoliers, prostitutes, aging revolutionaries, circus stars, bank employees, beggars and trash collectors.

Most people the couple met along the way were warm and welcoming — and surprisingly spontaneous. But Ms. Fischer and Mr. Braschler did run into trouble, logging three arrests during their journey. In a place like China — here follows a travel tip from the experienced — it is best to be discreet when using a 4-by-5 camera equipped with a flash and a soft box to make a portrait of a trash collector.

“People loved it at the beginning,” Ms. Fischer said. “You have to imagine — dozens of people surrounding us while we shoot.”

Mathias Braschler and Monika Fischer

But when they tried to make a portrait of a truck mechanic in Xinmin, Liaoning Province, bystanders agreed that the man was too dirty; he would give an international audience a negative impression of the country.

Who called the police?

“Many of them,” Ms. Fischer said. “They all had cellphones.”

In Shenzhen, a metropolis north of Hong Kong, Ms. Fischer and Mr. Braschler exercised discretion when they came across a beggar with a one-legged monkey (Slide 17).

“We suggested, ‘Why don’t we go to a place that’s a little more quiet?’ ” Mr. Braschler said. “In a way, you really have to adapt the way you work in China compared to the U.S.”

Yet they were overwhelmed by the beauty — and the range — of the physical landscape, mountains and all. “It was just so much to digest,” Ms. Fischer said.

They researched each province to familiarize themselves with its history, culture and characteristics, hoping to inform their portraiture. They traced out a route that would take them where they wanted to go over about eight months.

In January 2007, the Chinese government opened up most of the country to journalists, preparing for the Beijing Games. Mr. Braschler and Ms. Fischer started shooting that June and finished in January 2008.

The success of past portrait projects — “About Americans” and “Faces of Football,” for which they won a World Press Photo award in 2006 — gave Ms. Fischer and Mr. Braschler the support of various partners: Stern in Germany, Vanity Fair in Italy, Figaro Magazine in France and The Guardian in the United Kingdom.

The book “China” was released internationally late last year. Around the same time, the work has been shown in Germany and Switzerland — the subject of their current, yearlong road-tripping venture for the country’s tourism board.

Mr. Braschler, 43, and Ms. Fischer, 41, move between Zurich and New York with their infant son. Her background is in opera, where her work as a stage director schooled her in framing and lighting.

“I just thought it was so much more interesting to see the real people out there,” she said. “So I started going along with him, and more and more we started to work together.”

Across China, she worked with subjects to come up with poses that fit both their personalities. It was, after all, about the people — most of whom did not speak English.

Ms. Fischer recalls a beautiful woman in Yunnan, the oldest living participant of the Long March (Slide 11). They spent the day together. “She invited us into her room,” Ms. Fischer said. “She said she’s still very convinced of communism.”

Though everyone’s story was compelling, Mr. Braschler said the young star of a traveling circus (Slide 20) stood out in his mind. “The motions she went through, being very proud,” he said. “She was really quite special.”

Mathias Braschler and Monika Fischer

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