It won't be long -- if it hasn't happened already -- before every image becomes potentially suspect. False images have the potential to linger in the public's consciousness, even if they are ultimately discredited. And just as disturbingly, as fakes proliferate, real evidence, such as the photos of abuse at Abu Ghraib prison in Iraq, could be discounted as unreliable.
And then there's the judicial system, in which altered photos could harm the innocent, free the guilty, or simply cause havoc. People arrested for possession of child pornography now sometimes claim that the images are not of real children but of computer-generated ones -- and thus that no kids were harmed in the making of the pornography (reality check: authorities say CG child porn does not exist).
In a recent civil case in Pennsylvania, plaintiff Mike Soncini tussled with his insurance company over a wrecked vehicle, claiming that the company had altered digital photos to imply that the car was damaged before the accident so as to avoid paying the full amount due.
In Connecticut, a convicted murderer appealed to the state supreme court that computer-enhanced images of bite marks on the victim that were used to match his teeth were inadmissible (his appeal was rejected). And in a Massachusetts case, a police officer has been accused of stealing drugs and money from his department's evidence room and stashing them at home. His wife, who has accused him of spousal abuse, photographed the evidence and then confronted the cop, who allegedly destroyed the stolen goods. Now the only evidence that exists are digital pictures shot by someone who might have a motive for revenge.
"This is an issue that's waiting to explode," says Richard Sherwin, a professor at New York Law School, "and it hasn't gotten the visibility in the legal community that it deserves."
So far, only a handful of researchers have devoted themselves to the science of digital forensics. Nevertheless, effective, if not foolproof, techniques to spot hoaxes are emerging -- and advances are on the horizon. Scientists are developing software, secure cameras and embedded watermarks to thwart image manipulation and sniff out tampering.
Adobe and Microsoft are among the private funders, but much of the work is seeded by law-enforcement agencies and the military, which face situations in which more than just reputations are at risk. (Maintaining the integrity of the chain of evidence is of utmost importance to law enforcement, and the military is concerned about the veracity of images arriving from, say, Iraq or Afghanistan. Does that picture really portray Osama bin Laden? Are those hostages in the grainy video really American soldiers?)
But Farid and other experts are concerned that they'll never win. The technologies that enable photo manipulation will grow as fast as the attempts to foil them -- as will forgers' skills. The only realistic goal, Farid believes, is to keep prevention and detection techniques sophisticated enough to stop all but the most determined and skillful. "We're going to make it so the average schmo can't do it," he says.
Faked photography has a long and inglorious history. In the 1870s, "spirit photographs" were the rage -- images of dead loved ones were combined with shots of living kin taken during séances and passed off by charlatans as proof of the spirit world. During the Cold War, the Russian and Chinese governments were notorious for their propaganda fakes; discredited officials were routinely removed from state photographs.
But the human eye isn't easily fooled: Hardwired for pattern recognition, people can readily spot subtle inconsistencies. Verification experts look for these anomalies -- differences in light, shadow and shading; perspective that's out of whack; and incorrect proportions, such as one person's head being unnaturally larger than another's.
Thanks to the digital nature of today's photos, though, never has it been so easy to fool the eye with high-quality forgeries, reshaping reality with a few clicks of a mouse. A digital camera contains a light-sensitive plate covered with tiny sensors called cells, which receive photons of light when the shutter opens. The cells collect photons like raindrops in buckets, then convert them into electrical charges, which are amplified and themselves converted from analog to digital form.
In every digital image format -- JPEG, TIFF, RAW -- a photograph is really just a data file consisting of strings of zeros and ones. A program is required to translate that binary code into pictures, much the way your TV converts digital cable or satellite signals into moving images.
Such programs abound. Five million copies of Adobe Photoshop have been licensed, iPhoto is bundled with all new Apple computers, and Picasa 2 is available free from Google. This software not only interprets the original data; it's capable of altering it -- to remove unwanted background elements, zoom in on the desired part of an image, adjust color, and more. And the capabilities are increasing.
The latest version of Photoshop, CS2, includes a "vanishing point" tool, for example, that drastically simplifies the specialized art of correcting perspective when combining images, to make composites look more realistic. Nor are these programs difficult to master. Just as word-processing programs like Microsoft Word have made the production of professional-looking documents a cakewalk, photo-editing tools make us all accomplished photo manipulators fairly quickly. Who hasn't removed red-eye from family pictures?