Everyone knows the saying that the camera never lies. What is less well-known is that the man who coined the phrase, almost a century ago, added a rider. "While photographs may not lie," the great American documentary photographer Lewis Hine said, "liars may photograph".
They have been at work ever since, as was seen this week with the fake snap of John Kerry which caused a stir in the United States. It purported to show him associating in the 1970s with the film star Jane Fonda, who is still widely reviled in the US for her visit to the enemy capital, Hanoi, during the Vietnam war. Many still see it as the act of a traitor.
This was not the kind of publicity the Democrats' leading presidential candidate needed. It was, we now know, doctored. But it fooled many US citizens and some British newspapers.
They should, it is easy to say with hindsight, have known better. For the black art of photographic manipulation has been with us for a long time.
True, it is more sophisticated than when two young girls in Yorkshire launched what was to become one of the greatest hoaxes of the 20th Century. They claimed to have photographed the fairies at the bottom of their garden.
The pictures, taken in the summer of 1917, turned out to be paper illustrations, cut from a popular children's book, Princess Mary's Gift Book, and held up with hatpins. But it was a stunning deception. The Cottingley Fairies fooled many people, including the eminent self-styled detective Sir Arthur Conan Doyle.
The techniques of trickery have evolved over the years. At first a bald lie sufficed. In Russia at the end of the 19th century a French lumiére operator, finding that audiences at the Cinématographe craved film of the Dreyfus scandal, strung together shots from a number of films he had on hand - a group of French soldiers with an officer, an imposing building in Paris, and a ship at sea - to create the desired effect.
But then came physical interference with the photographic print. Abraham Lincoln was a pioneer here, asking a photographer to retouch a portrait to shorten his neck and make him appear more youthful. The result, he insisted, assisted his electoral victory.
Next Edwardian spiritualists discovered that double exposure would produce photographs of spectral relatives hanging in the air behind their grieving clients.
In the 1930s supporters of the anti-Communist zealot Joe McCarthy turned to careful scissorwork to undermine one of his earliest critics - Senator Millard Tydings - appearing to make him unnaturally friendly with the leader of the American Communist Party. Evidence that cut-and-paste was in those days an international phenomenon is there for anyone who cares to inspect the Daily Herald photo archives now lodged with the National Museum of Photography in Bradford. But if the techniques evolved, the formulae of fraud are fairly constant. So are the motivations. The press office of 1980s' film star Robert Redford used to issue instructions that his photographs should be retouched - particularly "the veins on his nose" and "the area around the throat and neck".
Some stars don't even have to ask, as with the GQ magazine cover shot of Kate Winslet which was digitally "stretched" to make her look thinner and sexier. Then there is mischief. It now seems pretty clear that the quintessential photo of the Loch Ness monster, allegedly shot in 1934 by a London gynaecologist, was a hoax made from a toy submarine to which a neck of plastic wood had been fastened. A similar sense of prankishness is today to be found behind internet japes like doctoring images of George Bush so that he is holding a children's book upside down, or looking through binoculars with the lens caps on. But the main motivation behind picture manipulation is politics of a darker kind. It always has been. During World War I many newspapers showed faked propaganda photographs of Kaiser Wilhelm cutting off the hands of babies. Soviet archives were filled with shots in which "disgraced" individuals, like Tolstoy and Molotov, had been airbrushed from party portraits on the orders of Stalin. In the West pictures of the German filmmaker Leni Riefenstahl were doctored to place her standing next to Hitler, to reinforce the anti-Nazi view that she was too close to the dictator. Manipulated photos can reveal hidden agendas. Time magazine came in for criticism for being racist when its cover featured a grim mug shot of OJ Simpson - looking darker and more sinister than in the same picture on the cover of Newsweek.
The official police photo turned out to have been electronically manipulated to create what Time, in small type on an inside page called "photo illustration".
And in Britain The Daily Mail was taken to task by Reuters when two of the agency's photographs of the singer Michael Jackson - taken the day after he dangled his baby son from a window - were merged under the emotive headline "Is he fit to be a dad?" To make the image even more distorted, Jackson's security personnel had been painted out of the image.
Modern computer technology has only made such cavalier decisions easier to make - like when the National Geographic used an early Scitex computer digitiser to move one of the Great Pyramids of Egypt so that it would fit the magazine's vertical cover format.
Russell Roberts, senior curator at the National Museum of Photography said: "It is possible, with careful scrutiny, to detect some of this."
"If you look at the Kerry/Fonda picture you can see there are two different light sources on the two figures. There are shadows on the side of Fonda's face, but not Kerry's; the light falls differently on the wrinkles in their clothes," Mr Roberts said. Yet such analysis is not uncontroversial.
Not everyone is convinced by the website of the French astronomer who says that the shadows in the pictures of American astronauts on the moon prove that the Apollo lunar mission was a fake and that the pictures were codded up in some US desert.
Still, truth is not always the final prejudice. Barbara Warnick, Professor of Media Criticism at the University of Washington, and author of Critical Literacy in a Digital Era says: "Events have shown that parodic activity can be a consequential factor in national [election] campaigns."
The task of campaign managers has nowadays shifted to "reviewing what is out there and trying to contain it."
Until now it has been Mr Bush who has been the butt of the internet photo parodies - with shots of him cuddling up naked to Al Gore, earnestly studying "Anchor Politics for Dummies", dressed in women's clothes, or incapable of holding a children's book the right way up. His aides have been so worried that they had lawyers send a cease-and-desist order to one website and eventually filed a complaint with the Federal Election Commission.
Which means that Senator Kerry can comfort himself with one thought. The faked photos of him and Ms Fonda show that he must have got the Bush camp really worried.Reuse content