Below are some close-up images of John Travolta. Which one is the most "classic" or identifiable as Travolta?
Every photo presents unique variations of hair, expression, angle, age, and lighting. Sometimes the person hardly looks like themself. If you have ever painted a portrait likeness, you know that it helps to have a lot of photos of the individual. If you copy just one piece of reference, you may not get a recognizable likeness at all.
So which one is the classic Travolta for you? If you chose the one in the center, there's a good reason for it. It's not a photo at all, but rather a computer average of the other photos.
Computers can take a set of photos of a person and blend them into a single average face, erasing vagaries of illumination, perspective, and expression.
Here is a set of those averaged faces of celebrities. They have polygonal borders, but those polygons at least keep some sense of shape and proportion. To my eye, they're almost all instantly recognizable (unless I didn't know them at all). I'd guess that they're probably more identifiable than any single photo taken at random.
The scientists who did this work discovered that these averaged faces are also far more recognizable to A.I. facial recognition systems than are random photos. As the authors put it "the simple process of image averaging can dramatically boost automatic face recognition." Sometimes the averaged faces boosted the success rate from 40% to 100%.
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