A good example was The Guardian's front-page photograph (above right) last week of the Chancellor on Budget day under the headline "Brown's conjuring trick". Gordon wasn't the only magician at work that day - The Guardian's picture desk was also busy.
The Guardian was the only newspaper to snap the news image of the day: Mr Brown standing alone outside No 11 Downing St, holding up his famous red box. Everyone else settled for a picture of Mr Brown accompanied by at least one of the young workers who had made his brand new leather box (except for The Independent, which cut out Mr Brown and his box and stuck him on a white background).
It was not, however, the skill of The Guardian's photographer that secured this image but the work of its process department, which used a computer system to paint out the young woman standing next to Mr Brown.
The next day, the paper ran a muted apology for the deception which the editor, Alan Rusbridger, described as "an example of over-enthusiasm". The paper had not removed a real person but merely "the hair apparently growing out of Gordon Brown's hand". Mention was not made of the rest of the woman's body, which must have appeared in the original picture below the red box.
The technology available to picture editors is now so powerful that every newspaper, including this one, confronts daily the temptation to "tidy up" photographs for its news pages. The Independent on Sunday, for example, ran a photograph of a beautiful snowy lane one day last winter. The original print showed a nasty black hole where steam from a man-hole had melted the snow, but a couple of minutes at the computer and the black was blanked out. The editor who made the changes later felt rather guilty and would think twice before taking such action again.
Photographers have always doctored pictures - even in the darkroom. Some changes are considered acceptable - darkening skies, for example, to capture a mood - and others are not. The Stalin-esque air-brushing of unwanted characters or the tabloid-esque addition of bimbos to photographs is clearly wrong. The problem is that the new technology - Adobe Photoshop - in which negatives or prints are scanned to create a digital image on a computer screen, allows changes that might once have taken days in a darkroom to be made in seconds. And the reader sees no trace of the manipulation.
The Sun last week ran a picture of Gordon Brown in a Union Jack dress and a ginger wig to show its readers what "Chancellor Spice" would look like. But then, as The Guardian's picture editor, Eamonn McCabe, notes, "They've got a licence to do that because they're a tabloid. The qualities don't have a licence to do that, because people believe what they see."
And then there is the Evening Standard, which got into hot water by doctoring a photograph of John Prescott and his wife Pauline so that they appeared to be drinking champagne rather than beer. The reason for doing so was apparently to justify the caption "champagne socialist". Max Hastings, the editor, apologised to Mr Prescott, saying: "I deplore any alteration of photographs in this way."
Picture editors seem to agree, however, that "cosmetic" changes are justifiable. Both Eamonn McCabe and David Swanborough, picture editor of The Independent, admit to lightening or darkening prints. "If you look at Wimbledon," McCabe says, "some people like a lush green and others like a lighter green." And the Photoshop programme can give you what you want.
"Taking people out of pictures or putting things in can't be right," he adds. David Swanborough says: "We wouldn't alter the truth of a photograph." The Independent does print photo-montages, but they are always clearly labelled as such.
One reason that the Gordon Brown image so annoyed other photographers was that the Chancellor specifically and deliberately refused all requests to move away from the young workers on Budget day and have his picture taken alone. "The photographers gathered in Downing Street booed him," Swanborough says. "It was clear that his intention was to be photographed with these people."
Tom Stoddart, a photo-journalist who still prints his pictures in a dark room, where enhancement occurs in the printing process, says he would welcome a system of labelling photos that have been touched up electronically. "It is a very difficult area, because newspapers now all do it to a certain extent," he says.
But Horst Faas, photo editor at the Associated Press in London, Pulitzer Prize-winner and veteran of Vietnam, says that his agency has a very strict policy on electronic manipulation. "We are under orders never to remove any of the contents of a photo, never to remove anything that makes a photo look not as good," he says.
"We use Photoshop to crop and to remove blemishes, like dust or scratches. We also use it to improve colours if there is an outside influence that affects the picture." The latter might include photos of skiing at night, for example.
But the AP has the capacity to undo electronic enhancement of any image wired in by a photographer, and its editors do double-check images to see what changes have been Photoshopped. Any photographer found to have breached the rules would be dismissed, Mr Faas says, because, "A photograph should be a real document, a document that readers can trust"nReuse content