they do it with mirrors
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Rembrandt Probably Traced His Self-Portraits With Mirrors And Lenses
Rembrandt was renowned for his masterful use of light and dark contrasts, and the precise proportions in his paintings and etchings. Now a British artist claims the 17th century painter likely used combinations of mirrors and lenses to project images onto a drawing surface to create them — especially his famous self-portraits. It’s the latest…