It’s interesting how surfaces reflect light. Take, for instance, butterfly wings: they aren’t colored, but covered with thousands of tiny prisms, each perfectly aligned and designed to reflect a different frequency of light. The result of this lattice of prisms is glowing color, or what physicists call ‘structural color’.
Structural color is sometimes used in car paint too, when paint particles are aligned using electric charges so that they’re all oriented the same way in space. When light hits these particles, it is reflected uniformly and the car’s color is rich and glowing like butterfly wings.
There’s another artists’ trick using light called ‘anamorphosis'; it’s when objects are stretched so that they only look natural when viewed at an angle, or through a mirror, or in a convex lens. The following picture, by István Orosz, describes the physics and math behind the ‘stretch’.
Why would an artist want to obscure images using anamorphosis? The technique has been around a long time, but gained popularity during the Renaissance, when artists like Leonardo drew his famous eye (1485); when Hans Holbein the Younger worked at the court of Henry VIII (1533); and later in Baroque architectural murals, when Andrea Pozzo painted the ceiling of the Church of St. Ignazio in Rome (1625-50).
Anamorphosis didn’t regain artistic popularity again until the 20th century; starting with the work of iconoclasts like Marcel Duchamp and The Bride Stripped Bare by Her Bachelors, Even; then attracting a whole crowd of artists after WWII.
Why would these two time periods, the Renaissance and the twentieth century, see a flowering of anamorphism in art? They were both very polarized times, when a new elite consolidated power after a period of struggle. They were both times when a superfluity of money (amongst the ruling class) was available to finance the arts. Also, both were times of extreme religiosity, although the twentieth century crowd might not like to admit it.
Anamorphosis is a self-conscious artistic technique that is motivated by an understanding of how to manipulate the viewer’s perceptions- perhaps even a desire to appear ‘one step ahead’. Art patrons who support this type of art are very conscious of their role in leading public perceptions, maybe they’re more conscious of their power than they are conscientious about how they use it. Nobody would call Henry VIII a man ‘for the people'; you can debate what good came from the power-politics of the Protestant Reformation; and people will certainly debate the ‘progressive’ policies of the 20th century. Whatever your conclusion, the movers-and-shakers of these times had immense faith in themselves and moral certitude- as I said, these are both highly religious eras, and the art of the time reflects that.