Perhaps just as critical in determining the veracity of a photo is reviewing its context. Who published it and what story is the source trying to tell? It is election season, after all, and everyone has their own agenda.
Former Adobe vice-president Kevin Connor founded Fourandsix Technologies to develop a better system of fact-checking photos. The first thing he suggests people do in photo forensics is reverse-Google the photo to see if it has appeared online before. If you identify a match, check for edits. You should also, advises Connor, research original publish dates.
“For example, it's not uncommon for an image to appear on social media claiming to be of a crowd in a recent protest, but reverse image searches then reveal that the image was actually taken in a completely different city years earlier.”
Connor developed the website izitru.com to help streamline the verification process. Photographers can upload their original files to its database to authenticate their images.
Last but not least, fact-checkers can run images through error-level analysis (ELA) on websites like fotoforensics.com. An ELA scans the compressed areas to reveal the modified parts of the image. But remain wary of drawing any conclusions.
“At best, ELA might be useful for directing your attention to certain areas of the image that may deserve future scrutiny, but you shouldn't make any final conclusions based on ELA alone.”
In all cases, the best thing to do in determining image authenticity is to use common sense. Look at an image for clues. The below example shows a woman wearing a laughable t-shirt at a Clinton campaign rally, only to be voided by the original untouched version shared on Twitter.
Online images are innocent until proven guilty. Use your best judgment to sort the retouched marketing images, most notably in fashion and food ads, from the the news. But when it comes to real stories, we can't afford fake. Media outlets like the AP forbid manipulation:
“AP pictures must always tell the truth. We do not alter or digitally manipulate the content of a photograph in any way. The content of a photograph must not be altered in Photoshop or by any other means.”
PS: The below image of 300 dead reindeer struck by lightning in Norway last week initially looked photoshopped. But the Norwegian Environment Agency confirmed the report, even capturing a video of the aftermath.