Since its introduction in the mid-19th century, photography has shaped public perception of U.S. presidents during their lifetimes and long after. So American presidents, always among the most photographed people on earth, learned to use photography to mold how they were presented, says Cara Finnegan, a professor of communications at the University of Illinois at Urbana-Champaign.

In her book, Photographic Presidents: Making History from Daguerreotype to Digital, Finnegan traces U.S. presidents’ evolving relationship with photography.

As technology changed how photographs were produced and disseminated, presidents adapted their efforts to present a positive image. The complex relationship dates back to photography’s earliest form: the daguerreotype.

A new form of portraiture

John Quincy Adams, who served as president from 1825 to 1829, considered the daguerreotype a “wondrous” invention. Presented by inventor Louis-Jacques-Mandé Daguerre in Paris in 1839, the process used mercury vapor to create images on a plate. By the early 1840s, photography studios had cropped up in most major cities, and people flocked to have their portraits made.

Adams was among them. But having sat for painters and sculptors his whole life, the sixth U.S. president had a fraught relationship with portraiture. “He believed portraits should be an index of someone’s moral character — what he called ‘true portraiture of the heart,'” Finnegan told ShareAmerica. “And he felt that photography could not capture that.” Adams described his photographic portraits as “hideous.”

An 1843 daguerreotype, taken 14 years after Adams left the White House, is the earliest surviving photograph of a U.S. president. An 1849 daguerreotype of James K. Polk, the 11th president, is the earliest surviving photograph of a sitting U.S. president.

Abraham Lincoln was photographed more than 120 times, mostly in the ambrotype format. The process, common in the 1850s, still used chemicals to create an image on a glass plate but allowed for portable equipment. Photographers left their studios, traveled and produced compact portraits known as “cartes de visite.” By the mid- to late 1860s, the ambrotype was succeeded by the more economical tintype, printed on iron.

Lincoln, the 16th president, sat for his last official portrait in February 1865, just weeks before his assassination. The resulting “cracked plate” image, made on glass that was accidentally damaged, captures a careworn president wrestling with the fate of a nation in the midst of civil war.

The rise of photojournalism

Dry plate photography, invented in 1871 and popularized in the 1880s, further enhanced photographers’ mobility. New gelatin-coated plates could be stored for a month before exposure, freeing photographers from messy and inconvenient production processes.

New York entrepreneur George Eastman launched a dry plate manufacturing company and began experimenting with and producing film in the mid-1880s. In 1888, Eastman’s company “introduced film rolls sufficient for 100 exposures — mounted in a small box camera called the Kodak,” according to the National Inventors Hall of Fame.

Changes in technology brought presidents both greater publicity and increased risk of unflattering images. While presidents were once photographed only in photographers’ studios, Finnegan said, “anyone out on the street could now capture a photo of you.”

In the early 20th century, the advent of newsreels and the rise of photojournalism brought presidents even greater visibility. Theodore Roosevelt, who became the 26th U.S. president in 1901, “was savvy about arranging photo opportunities,” Finnegan said.

In the 1920s, Warren Harding, the 29th president and a former newspaperman, and his successor, Calvin Coolidge, also embraced “photo ops.”

Capturing the president’s image became a full-time job in 1961, when President John F. Kennedy made Cecil Stoughton the first official White House photographer. Previously, military photographers had photographed White House events and captured candid moments of first families.

With the exception of Jimmy Carter, every U.S. president since has had an official photographer. After taking office in 1963, Lyndon Johnson gave photographer Yoichi Okamoto unprecedented access, and Okamoto’s work still inspires presidential photographers today, Finnegan said.

Barack Obama’s election in 2008 coincided with increasing social media use in the U.S. The 44th U.S. president embraced the new platform, Finnegan said, creating a social media team and a White House Flickr page to engage global audiences.

Pete Souza, White House photographer for both Obama and Ronald Reagan, the 39th U.S. president, had free rein to take behind-the-scenes photographs, as Okamoto had, Finnegan said.

“Circling back to John Quincy Adams and his notions of ‘portraiture of the heart,’ the Johnson and Obama photos do, in fact, reveal quite a lot about the characters of these presidents.”