“To the attentive eye, each moment of the year has its own beauty, and in the same field, it beholds, every hour, a picture which was never seen before, and which shall never be seen again.” — Ralph Waldo Emerson
The way we look at certain objects affects how we perceive it. Sometimes we are presented with two different images in the same picture but we only see one image and we disregard the other. An optical illusion is distinguished by visually perceived images that are deceptive. It occurs when the brain makes a wrong interpretation of what the eye actually sees. In optical illusions, the brain mistakes part of what it sees for something similar.
Some well-known illusions are the Rubin Vase, M.C. Escher’s Ascending and Descending illusion. These illusions are under cognitive illusions assumed to arise from stored knowledge about the world. This idea was first suggested in the 19th century by the German physician and physicist Hermann Helmholtz.
Ambiguous illusions are pictures or objects that draw out a perceptual “switch” which provides alternative interpretations between two figures. The Rubin Vase, also known as Rubin face or Figure-ground vase, is a well-known example. It was developed by Danish psychologist Edgar Rubin. The illusion presents the viewer a mental choice of two interpretations, each one valid.
The viewer often sees one but realizes there is another valid interpretation after some time. When the viewer attempts to simultaneously see the second and first interpretations, he suddenly cannot see the first interpretation anymore. No matter how hard the viewer tries, he simply cannot encompass both interpretations simultaneously because one blocks off the other.
Distorting illusions are the most common and are characterized by distortions of size, length, or curvature. A striking example is the famous Muller-Lyer illusion. One variation of the illusion consists of two arrow-like figures, one with both ends pointing in and the other with both ends pointing out. Asked to judge the length of the two lines, viewers say the inward pointing pair is shorter. The two vertical lines are actually the same length. A possible explanation is that one sees the lines as three-dimensional. Another possible explanation is that the line with arrows pointing outwards may simply appear longer because the arrows themselves extend past the line.
Paradox illusions are generated by objects that are paradoxical or impossible. Ascending and Descending “Tessellation” tessellations. The Ascending and Descending lithograph depicts a large building roofed by a never-ending staircase. Two lines of identically-dressed men appear on the staircase, one line ascending while the other descending. Two figures sit apart from the people on the endless staircase: One in a secluded courtyard, the other on a lower set of stairs.
Revolutionary and iconoclastic Spanish artist Salvador Dalí is one of the most important painters of the 20th century. He is best known for the striking, bizarre, and beautiful images in his surrealist works. Dalí had a life-long fascination with illusion, visual perception, and distortion. His best known work, The Persistence of Memory, was completed in 1931. Widely considered to be greatly imaginative, Dalí had a penchant for doing unusual things to draw attention on. Several of his works incorporate optical illusions. Dali was fascinated by the hypercube, a four-dimensional cube featured in the painting Crucifixion (Corpus Hypercubus).
The pattern of the floor tiles at the Basilica of St. John Lateran Rome creates an illusion of three-dimensional boxes. The Basilica of St. John Lateran is the cathedral church of Rome and official ecclesiastical seat of the Bishop of Rome. It is the oldest and it ranks first (being the cathedral of Rome) among the four major basilicas of Rome. It holds the title of “Mother Church” among Catholics. As the cathedral of the Bishop of Rome, it contains the papal throne (Cathedra Romana) and ranks above St. Peter’s Basilica in the Vatican.
Forced perspective, used primarily in filmmaking, is a technique that often employs optical illusion to make an object appear farther, closer, larger, or smaller than it actually is. It manipulates human visual perception through the use of scaled objects and the connection between them and the vantage point of the spectator or camera.
The final scene of the Oscar-winning classic movie Casablanca takes place at the airport in the middle of a storm where Rick Blaine (Humprey Bogart) sends-off Ilsa Lund (Ingrid Bergman) and her husband Victor Laszlo (Paul Henreid) to escape from Casablanca which was under the Nazi rule. The entire scene was actually shot in a studio. The film crew used a painted backdrop of an aircraft.
The movie also used people as flight crew using the technique of dwarfism. They were filmed standing next to the backdrop. The heavy downpour created inside the studio draws much of the viewers’ attention away from the backdrop and extras, making the simulated perspective less noticeable.