Wednesday, May 30, 2012
How to detect for purposes of trial a photoshopped picture from an unretouched one
From Law Technology News:
"A picture is worth a thousand words,” or so they say. Yet this expression only holds true if the photo in question provides evidence of a genuine person, place or object. If the image has been tampered with by using Photoshop or another image editing application, there's a strong chance that the picture isn't worth much more than the paper it is printed on.
While photographic evidence is one of the most effective means of eliminating doubt when preparing a court case, it's also never been more challenging to establish that a photo hasn't been tampered with. At trial, a photograph usually must be authenticated by someone who is familiar with what the image depicts and who can testify that the image accurately represents whatever it illustrates. The authenticator is often the photographer, but can also be anyone at all, as long as he or she is familiar with the subject matter of the image.
To save time and money, many attorneys would like to be able to detect obvious photographic tampering before calling in an expert. This a goal that most legal professionals can achieve if they have the desire and time, says Siwei Lyu, a State University of New York at Albany computer science professor who specializes in image forensics. "In today's era of digitally manipulated images, it's becoming increasingly difficult, although not impossible, to detect traces of photographic tampering, all that's required is a discerning eye and the appropriate software tools," Lyu says.
Examining a photograph for unusual qualities is the first step in tampering detection. "One of the best ways to detect manipulation is to look for lighting oddities," says Tim Bradley, an intellectual property attorney at Coats & Bennett, a Cary, N.C., law firm. "For example, whether shadows are absent or incorrectly cast, or whether the light reflecting of peoples' eyes is not consistent in an image." Bradley also suggests looking for "orphan" shadows and reflections created by apparently invisible objects. "That too is a good indication of manipulation," he says.
"Knowing how to read light sources and shadows is the first step; that's usually the first giveaway," says Rick Kiesel, a graphics designer for QCI Direct, a home products marketing company located in Rochester, N.Y. But he adds that skeptical observers also need to keep an eye peeled for a variety of other clues, including the levels of color density and hue, as well as evidence of blurred edges on objects and figures, blurring in odd spots and a general lack of detail across entire images or within specific areas.
Continuing reading here for more tips and advice on how to spot fake photos.