Pareidolia is one of the main reasons ordinary shapes in photographs can look far more significant than they really are. It's a perceptual effect rather than a camera issue, and it happens when the brain tries to organise random patterns into something familiar. Faces, figures and silhouettes are the most common examples, especially in photographs taken in low light or in places where people already expect to see something paranormal.

Our brains are exceptionally quick at spotting human features, even when they aren't there. A combination of shadows, reflections, digital noise and uneven lighting can accidentally line up in a way that suggests eyes, a head or the outline of a body. Nothing unusual has appeared in the environment - the photograph is simply giving the brain enough ambiguity to "complete" the image with something meaningful.40Pareidolia is at its strongest when an image contains low detail, uneven lighting, or complex patterns....