"False Perspective" (1754) by William Hogarth, the scene looks normal until you look closely. For example, the woman leaning out the window cannot possibly be lighting the man's cigar. Also, the bird in the tree is almost as big as the tree. Finally, look at the sheep. They get larger as they are walking away instead of smaller. An optical illusion is a phenomena where one seems to see something that doesn't exist or with another perspective. It is also called visual illusion and is categorized by visually apparent images. An optical illusion is basically a visually misleading image interpreted by the brain inaccurately. There are three main types: literal optical illusions that create images that are different from the objects that make them, physiological ones that are the effects on the eyes and brain of excessive stimulation of a specific type (brightness, color, size, position, tilt, movement), and cognitive illusions, the result of unconscious inferences.