Spotting the Photoshop fakes

Posted on 13 May 2010 at 15:18

When elements are added to a photograph, said Farid, inconsistencies develop. The lighting is different: one person may be lit from one side, while the other is lit from the front by multiple lights. It isn’t only the direction of lighting that can be problematic: lights can have varying colours or brightness.

“Your brain is very bad at detecting those inconsistencies,” said Farid. “We’ve developed a series of tools that can measure in an image the lighting environment in which a person was photographed, and then look for inconsistencies.” Farid’s software, which is still under development, is “getting pretty good” at automatically detecting relatively small differences in lighting.

Another way of removing detail from a picture is with Photoshop’s Clone brush, which copies pixels from one part of an image and replicates them over another part. Some photographers use the Clone tool to remove specks of dust from their images.

In the case of Adnan Hajj, the Clone tool was used to make a plume of smoke appear larger than was the case. Would Farid’s software have detected Hajj’s forged images? Farid is unequivocal. “Yes, but also it was a very clumsy manipulation. I think if he was a little bit better people wouldn’t have noticed visually, but we probably would have,” said Farid. The same goes for Iran’s non-launching missile image.

However, imaging professionals are sceptical that their picture editors will be replaced as a crucial line of defence against forgeries. Hugh Pinney from Getty Images said, “I can see a point where you could run a picture through a bit of software and it will give you a history of what’s happened to it,” but that he would “rather put my faith in human beings”.

Turi Munthe from Demotix agrees, raising the spectre of a photographic arms race, in which determined forgers come up with ways to outwit the technology employed to stop them. Hany Farid is ready for the fight: a battle between developers such as himself and fakers is inevitable, he said, but isn’t necessarily something to fear.

“You don’t say that we’re not going to have antispam filters because we’re afraid it’s going to create an arms race,” he argued. “The faker will get better and better and better, but what we’ll do is make it harder, we’ll make it more time-consuming, and we’ll take it out of the hands of the amateur, so only a relatively small number of people will be able to do it.”

Criminal fakery
Even if picture editors are reluctant, Farid’s work has applications beyond the fourth estate. In 2009, he gave evidence in the High Court in Edinburgh as part of Operation Algebra, a hi-tech investigation that resulted in the conviction of eight paedophiles. “We routinely now have images, video, audio and documents in digital format introduced into a court of law as evidence,” he said. “It really matters that you can believe the evidence.”

Part of Farid’s evidence included what he calls “camera ballistics”, in which he proved that innocuous photos came from the same camera as another set of “horrific” images. Photoshop made the news in 2007 when 32-year-old Christopher Paul Neil, a Canadian paedophile, attempted to conceal his identity using Photoshop’s Swirl tool. His relatively simple photographic deception was undone by German experts, and he was promptly arrested in Bangkok.

Ironically, having played a major role in making faked photos accessible to photographers and the public, Adobe itself may be the key to the new technology that will defeat the criminals and other scammers.

Farid claims that Adobe’s financial support of his work is no-strings attached, but that the company is concerned that its product is being used in “nefarious” ways. “I think Adobe sincerely worries about that. I don’t think it wants its name to be used in the pejorative.”

Author: Dave Stevenson

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