Abraham Lincoln: The enduring images
When John Wilkes Booth crept into the presidential box at Ford's Theater and shot Abraham Lincoln on 14 April 1865, he had no trouble recognising the man he had come to kill.
That was thanks to photography - a technology that was then still in its infancy but would come to dominate the way all politicians have presented themselves ever since.
"Lincoln was the first president born in the photographic era," says Paul Tetreault, director of Ford's Theater in Washington.
"He was very aware of the importance of photography. But unlike our public figures today who have the $700 haircut and the right suit, I don't think Lincoln cared about that. He was very conscious of his shortcomings in the looks department and he didn't shy away from that."
On 27 February 1860, Lincoln addressed a large audience in New York where he was photographed by Mathew Brady - a pioneer of American photography. Brady pulled up Lincoln's collar to improve his appearance and the image was subsequently reproduced and copied by newspapers and magazines.
"That photograph established Lincoln not as a hayseed or bumpkin but as a sober, respectable, powerful intellectual who could become president," says David Ward, senior historian at the Smithsonian's National Portrait Gallery. "Lincoln said that this was the photograph that made him president."
Brady and his colleague Alexander Gardner went on to photograph Lincoln many times and their images endure today. But modern perceptions of the 16th president have also been shaped by two eerie life masks.
The sculptor Leonard Volk created the first mask in 1860 as a model for a bust of Lincoln. Having just won the election, Lincoln was in good spirits and full of energy. But the second mask, made by another sculptor Clark Mills in February 1865, just two months before Lincoln was assassinated, shows a very different man.
The Civil War was coming to an end and the enormous toll taken by four years of conflict is etched into the lines of Lincoln's craggy face. His eyes are sunken, his hairline has receded and he has grown a beard which also makes him appear older.
"He looks exhausted," says Ward. "In fact, people frequently think the second one is a death mask because he looks so exhausted."
Lincoln himself didn't think he'd survive his second term because of his failing strength. The masks are the most vivid documentation of how he aged. They are also the closest we can get today to being face to face with Lincoln.
"The life mask is personal because it actually touched Lincoln's skin," says Ward. "You have an almost ghostly remnant of the president where the plaster was on his face for half an hour in February 1865. It's kind of spooky."
Life masks were rapidly going out of fashion when Lincoln's were made. They had been popular in America as the best way to disseminate a realistic likeness of people - particularly politicians who, without photography, had no other way of enabling people to recognise them. Paintings were distrusted as being too subjective and somewhat decadent in a society that was focused on forging a new nation and had little time for the luxury of art.
But almost two centuries later, the life mask - or something like it - could be making a comeback.
Barack Obama is the first president to have his features digitally scanned and printed to create an identical 3D portrait.
"It really is the modern day equivalent to those plaster casts of Lincoln's face," says Gunter Weibel, director of the Smithsonian's Digitization Program. "[Life masks] were the best way to create accurate representation at the time. This is the best way today. But the end goal is really the same - can we create a direct line to a moment in history? I think both methods achieve that."
And there's another link. The idea for the president's 3D portrait occurred while technicians were scanning Lincoln's life masks to create 3D printouts and make the objects more accessible online.
"We thought, what could happen if we could actually update that process using modern day technology and do that with a sitting president? And that's what we did with President Obama," says Weibel.
The process was far less arduous than being encased in plaster. President Obama sat on a mobile light stage in the White House while flashing lights and cameras captured high resolution data of his face. In just a few seconds enough information was collected to create an exact three-dimensional likeness.
As America's first black president, Barack Obama is probably also the most instantly recognisable - apart from Abraham Lincoln.
Paul Tetreault says Lincoln is second only to Jesus Christ in the number of books written about him. Lincoln's image is still being re-interpreted and analysed. Even the life mask at the National Portrait Gallery is a 1917 rendering from Volk's 1860 cast, which is kept at the National Museum of American History in Washington.
"People want to reach out to try to understand, who was this guy? Who was this man who by sheer force of his own power held this country together?" says Tetreault. "We all find some connection to him and that's why I think the image of Lincoln will last forever and ever."