Lighting changes the perceived shape of a face. Shadows can emphasize or conceal particular features. Camera lenses can subtly alter proportions. A photograph captured from one specific angle may make two people appear much more alike than they would if they were standing next to each other in person.
Hair, clothing and facial expression can complete the illusion.
That is why one photograph is rarely enough to establish someone’s identity.
It may be enough, however, to make millions of people look twice.
The Brain Is Built to Recognize Faces
There is also a psychological reason celebrity look-alikes catch our attention so quickly.
Human beings are exceptionally sensitive to faces.
We routinely identify people from combinations of features rather than measuring every detail individually. Once a face becomes extremely familiar, relatively small visual cues can trigger recognition.
Think about how quickly you can recognize a close friend or family member from across a room.
