Julius von Bismarck’s Image Fulgurator is a modified camera that’s capable of projecting images onto street furniture (a bench, wall, sign etc.) where they appear in the photos of strangers, but remain invisible to their eyes.

So how does it work? According to Wired, the “half guerrilla-art stunt and half homemade-gadget awesomeness” has a “slave unit on top which is triggered when it sees a flash fire. This triggers his own flash, which fires through the back of the camera, through a film slide containing his slogan and then on and out through the lens at the front. This works because a camera is pretty much a projector in reverse. And because the light-graffiti is fired at the exact same moment the unsuspecting victim takes a picture, it ends up in their photograph and paranoid mind ramblings result”.