Can Digital Photos Be Trusted?

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 sances 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?

Before the digital age, photo-verification experts sought to examine the negative-the single source of all existing prints. Today´s equivalent of a negative is the RAW file. RAWs are output from a camera before any automatic adjustments have corrected hue and tone. They fix the image in its purest, unaltered state. But RAW files are unwieldy-they don´t look very good and are memory hogs-hence only professional photographers tend to use them. Nor are they utterly trustworthy: Hackers have shown themselves capable of making a fake RAW file based on an existing photo, creating an apparent original.