A man is looking through the flame of a candle at two flowers, the coloring of which is reversed as in positive and negative views. 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. Johann Zahn (March 29, 1641 - June 27, 1707) was a German monk and author of Oculus Artificialis Teledioptricus Sive Telescopium (1685) which contains descriptions, diagrams, illustrations and sketches of both the camera obscura and magic lantern, along with various other lanterns, slides, projection types, peepshow boxes, microscopes, telescopes, reflectors, and lenses. He also designed several portable camera obscuras, and demonstrated the use of mirrors and lenses to erect the image, enlarge and focus it.