Seeing is no longer believing

The advertisement shows a photo of a smiling couple. Then right next to it sits the same photo, but this time the man is missing. "We can fix your photographs to match your life" reads the sign in the framing store.

Airbrushing individuals out of your life is not new. Joseph Stalin routinely erased personae non gratae from official photographs. As his dictatorship progressed, early communist comrades gradually disappeared to the point where Stalin's entourage started to look quite sparse at times.

Today, with the advent of inexpensive software, the manipulation of digital images is easier, faster, and harder to detect. As a result, the ethics of manipulation - the line between "improving" an image and altering it - are more vital to preserving public trust.

In photojournalism the rules are clear. To alter the content of a photograph "in any way that deceives the public" is wrong, says the digital manipulation code of ethics of the National Press Photographers Association.

Ideally, a photograph is the untouched, unmanipulated transcript of what was there. Except, says Larry Gross, everybody knows there are elements of selection built in. The co-editor of "Image Ethics in the Digital Age" lists cropping and the angle of the photograph as two other common means to alter editorial content.

For example, in April 2003, not long after the start of the war in Iraq, an iconic image of Saddam Hussein's statue being toppled in front of a crowd of cheering Iraqis was flashed around the news media and came to symbolize the justness of the war.

Shortly after, a series of photographs started to circulate on the Web showing the same shot and several others but with a wider angle. "You could see there was no crowd," says Mr. Gross, a professor at the University of Southern California's Annenberg School of Communication. "What looked in the first reports like this joyous crowd of Iraqis was in fact a very small number in a roped-off area." That fit with reports that this was a staged event with an artificially collected group, he says. What revealed the reality was the uncropped image.

In photography, "there is a real conflict between an ideology of unvarnished truth and the reality of a lot of varnishing," Gross notes. And the evidentiary quality associated with the medium is more threatened than ever by the digital revolution, he adds.

While manipulation is not restricted to massaging pixels, that still happens in photojournalism. A classic case two years ago ended with the firing of the photographer. Brian Walski, who was covering the war in Iraq for the Los Angeles Times, combined two photos taken moments apart to create a more striking image. He was caught when someone noticed a duplication in the picture.

Breaking that unspoken contract of trust with the public can be costly. It degrades the value of the publication, says Stephen Grote of the Art Institute of Atlanta. And as the Los Angeles Times director of photography, Colin Crawford, said at the time, "If our readers can't count on honesty from us, I don't know what we have left."

The public's image-naiveté is disappearing, however, as awareness grows of the ease with which a picture can be "Photoshopped" (now a verb from Adobe Photoshop editing software). Add to that the higher level of suspicion of institutions in general, says Gross, and it becomes more imperative to say, "We don't do that," and to have a zero-tolerance policy.

As the story of the photo of the statue illustrates, blogs and other forms of Internet communication have made it harder to get away with manipulation, because it's harder to contain information, Gross says.

One way of shoring up public confidence is to make the penalties greater - what Gross calls "show trials." The rapid firing of Mr. Walski, despite his 25 years of experience, is a case in point.

Yet the temptation to tamper remains. And nowadays, it is tampering the human eye can now rarely detect.

That becomes critical in the courtroom, where digital photographs are used as evidence, and in military surveillance, where satellites offer a view of the battlefield or tank battalions or mass burial sites.

In that vein, Hany Farid is trying to put some certainty back into photography. The computer science professor at Dartmouth College in Hanover, N.H., is developing computer algorithms that can detect when an image has been altered.

"We try to put ourselves in the seat of the forger," he says, and look at the types of manipulations a forger would do to make a convincing composite image.

For instance, when you splice two people together, one of them often needs to be resized or rotated slightly, by a process known as resampling. "That type of manipulation introduces very specific forms of statistical correlations in the image, which are not naturally present, and we can detect those," he says.

His group has written six algorithms to detect those statistical changes and is working on a half dozen more.

The algorithms don't work, however, if the forger uses a manipulation outside those six or if the image is compressed to a size where the statistical patterns that were introduced get destroyed.

There's no silver bullet here, Dr. Farid admits. "It's a bit of an arms race," he says, likening it to the virus and antivirus wars waging over the Internet. "It's tamper and tamper protection, and we can already predict who's going to win."

"We simply make it harder," he says. The average person with the average amount of skill is less likely to pull it off.

Yet trying to determine the integrity of a photo may be missing the point, says Gerald Richards, a retired chief of the FBI's Special Photographic Unit.

"Since the advent of photography, we have never been able to say a photograph is genuine," he says. "The only thing you can say with certainty is that it is not genuine."

"What makes it reliable," he says, "is the photographer who comes in and raises his hand and says, 'Yes, I took this picture and it is a true and accurate representation.' "

For police departments and the FBI, the digital medium has forced a more sophisticated protocol for handling photographs, he says.

Mr. Richards, who now runs his own forensic services company, was an expert witness in O.J. Simpson's civil suit, testifying for the prosecution about the photograph of O.J. allegedly wearing those infamous Bruno Magli shoes. He rebutted the 11 points of contention that it was a fake, he says, simply on the basis that "I could find nothing wrong with it."

In court, defining "manipulation" is difficult and depends on degree, he says. "Are we changing one little spot or are we changing the body of a person?"

The bottom line is that there is no true objectivity. Renowned photographer Edward Steichen recognized that, even before the advent of pixels. "Every photograph is a fake from start to finish," he said, "a purely impersonal, unmanipulated photograph being practically impossible."

Gross echoes that sentiment. "The mistake is to think that there is a pure stance."