Blurred, as if you squint: Albert Einstein.
Two pictures in one
A face in the lines
Squint, or step back from the screen. What do you see?
Albert Einstein.
Why? The black lines are a little thicker where the photo is dark. Close up, you see only the sharp lines; squinting blurs them, and what is left is the photo. It works like the hybrid image.
Picture: Orren Jack Turner, hidden in lines by Science Playground, Public domain · Wikipedia(opens in a new tab)