We’ve examined power photo retouching before, but how can you tell when a photo’s been altered? Frequent photo editors often acquire a knack for spotting fake photographs, but what about the rest of us? Scientific American offers several tips on how to spot faked photographs. Among them: look at how the light hits the various people and objects in the photograph—everything in the photo should have matching highlights and shadows indicating they were all photographed at the same time under the same light source. More in-depth scrutiny can reveal other “tells”—eyes often being the giveaway.