In June 2008, a number of news outlets, including the Los Angeles Times, BBC News and the New York Times, unknowingly ran an image of Iran's missile tests that included one missile too many.
An image showing four missiles was distributed by Agence France-Presse (AFP), which said that it received the image from the Web site of the Iranian Revolutionary Guard's media division. Later, however, The Associated Press distributed a similar image that included only three missiles.
The AFP retracted its version of the photo, saying that it had been "apparently digitally altered" by Iranian state media.
In August 2006, the Associated Press had to pull a photo when an editor added an extra set of hands on an Alaskan oil pipeline worker.
The photo captured a BP employee scanning a section of pipeline that had leaked 200,000 gallons of oil earlier that year. An editing error apparently gave the worker four hands instead of two.
In one of the most well-known and earliest examples of photo manipulation, National Geographic moved the pyramids in Egypt to make a vertical cover out of a horizontal photograph.
According to the National Press Photographers Association, the magazine referred to the change as the "retroactive repositioning of the photographer," explaining that had the photographer been in a slightly different position, he would have been able to capture the image naturally.
But to photojournalism ethicists, it still constituted a lie that damaged the magazine's credibility, as well of that of the entire news business.
As technology has changed what photo editors can do to images, it's also changed the way the public perceives them, Long of the National Press Photographers Association said.
"People don't look at pictures as though they were historical documents but as things that they want them to be," he said. "It's so easy, it's so pervasive, that the nature of photography has become liquid. And that is a very big threat to what we do in the news business, which is to try to document reality in pictures that are accurate. Once the accuracy goes, we have nothing left to offer."