OPTICAL ILLUSION and FOCUSES, 3D-PICTURES - Isn’t it interesting?
 Optical illusions by Akiyoshi Kitaoka 3D-pictures Illusions in the Encyclopedias & Dictionaries
 CLASSIC OPTICAL ILLUSIONS and VISUAL PHENOMENA
 Fraser spiral optical illusion The illusion is also known as the false spiral, or by its original name, the twisted cord illusion. The overlapping black arc segments appear to form a spiral; however, the arcs are a series of concentric circles. The visual distortion is produced by combining a regular line pattern (the circles) with misaligned parts (the differently colored strands)...
 Ponzo optical illusion The effect of the Ponzo illusion is often attributed to linear perspective. The upper line looks longer because we interpret the converging sides as parallel lines receding into the distance. In this context, we interpret the upper line as though it were farther away, so we see it as longer. In the three dimensional world, an object located farther away would have to be larger than a nearby object for both to produce retinal images of the same size. This explanation is often referred to as the perspective hypothesis...
 Cafe Wall optical illusion This illusion is created when offset rows of alternating dark and light tiles are surrounded by a visible line of mortar. Ideally, the mortar is a shade somewhere between the two tile colors. When the tiles are offset by half a tile width, the horizontal lines appear to slant diagonally, creating the appearance of wedges. The illusionary effect is affected by both the position of the tiles as well as the thickness and color of the grout in between them. If grout lines are removed, there is no longer any illusion of diagonal lines...
 Ebbinghaus-Titchener optical illusion The Ebbinghaus illusion (sometimes called the "Titchener illusion") is an optical illusion of relative size perception. In the best-known version of the illusion, two circles of identical size are placed near to each other and one is surrounded by large circles while the other is surrounded by small circles; the first central circle then appears smaller than the second central circle...
 Poggendorff optical illusion In the figure the diagonal line segments do not appear to be segments of a discontinuous straight line (collinear) when in fact they are. This illusion is known as the Poggendorff illusion. Several factors affect the degree of misperception experienced in this illusion. One such variable is the separation of the verticals: The greater the separation, the greater the illusion. In this experiment, separation of the verticals and the length of the diagonal segments are both manipulated...
 Rubber pencil optical illusion Take a pencil in his hand (you can take and a pen) and shake them as fast as possible, as shown in the figure. It creates the illusion that a pencil is bent, as if it were made of rubber ...
 Wundt-Fick optical illusion The illusion (inverted T), which is called the Wundt-Fick illusion at least in Japan, originates from A. Fick only, a physiologist who described it in his doctoral thesis in 1851- this is the first geometric-optical illusion. It was documented even before Oppel, in 1854 coined the term "geometrisch-optische Tauschung" and contributed several more patterns. Although he became a famous ophthalmologist, his son may be an even more famous ophthalmologist, as he invented the first contact lenses...
 Zollner optical illusion The Zollner figure is composed of a series of parallel, diagonal lines intersected by a number of short horizontal and vertical bars. The parallel lines appear not to be parallel at all; rather, they appear to converge and diverge from each other...
 Jastrow optical illusion The Jastrow illusion is a size illusion where two curved shapes of identical measurements are placed next to each other. When viewing the two shapes, one looks significantly larger than the other. When the positions of the two shapes are reversed, the impression of which is the larger is also reversed...
 Muller-Lyer optical illusion The Muller-Lyer illusion is an optical illusion consisting of a set of lines that end in arrowheads. The orientation of the arrowheads affects one's ability to accurately perceive the length of the lines. Like most visual and perceptual illusions, the Muller-Lyer illusion helps neuroscientists study the way the brain and visual system perceive and interpret images. Artists have also utilized the illusion to great effect in their works...
 Illusions of the impossible figures. How many bars do you see? f you count the number of bars using the squares at the front, you'll find that there are eight total. But is it really that simple? Count the bars again, but this time use the end of the bars farthest away from you. How is that possible? According to the puzzle's creators, there are actually only six complete bars. You have to look very closely to see it...
 Illusions of the impossible figures - 2 ***
 Hering optical illusion. Parallel Lines visual illusion. The Hering illusion is an optical illusion discovered by the German physiologist Ewald Hering in 1861. The two horizontal lines are both straight, but they look as if they were bowed outwards. The distortion is produced by the lined pattern on the background that simulates a perspective design, and creates a false impression of depth. Note that the thinner line appears more bowed than the thicker line...
 Grid optical illusion. Hermann grid illusions. Scintillating grid illusions. A grid illusion is any kind of grid that deceives a person's vision. The two most common types of grid illusions are Hermann grid illusions and Scintillating grid illusions. Illusions such as these, and others, provide a window onto the way the eyes and the brain work together in creating perception. Scientists attempt to peer through this window when they propose hypotheses about how perception is accomplished. Illusions can also help us realize that our own perceptions may be limited or different from those of another person viewing the same thing...
 Kanizsa Triangle optical Illusion When searching at the Kanizsa triangle, certain sees the structure concerning a white, equilateral triangle of the core to that amount appears according to occlude the shapes round it. The nonexistent gray triangle additionally appears according to keep brighter than the inclosure area, but into reality that has the same brightness so the background...
 Dynamic Luminance-Gradient Effect by Alan Stubbs For the primary effect, one should sit at a comfortable distance and then move forward toward the center of the figure. An interesting change in apparent brightness and to some degree form will result—what may be called a “here comes the sun” effect. By moving back and forth, this apparent change will repeat...
 Pinna-Brelstaff optical illusion The inner and outer rings of the concentric circles in picture appear to rotate against each other as the eye is moved continuously closer to the paper (looming) while the gaze is kept fixed on the central spot. Moving out again reverses the direction of the illusory rotation. Focus your eyes on the center of the picture. Draw close to the screen, then back again - the circle will rotate in opposite directions...
 Pinna-Brelstaff-Spillmann optical illusion ...
 Enigma - Leviant optical illusion ...
 Optical illusions and delights from Akiyoshi KITAOKA
 VOLUMETRIC IMAGES 3D-PICTURES by Julian Beever - On the sidewalk with chalk

 OPTICAL FOCUSES and MYSTERIES - Amazing things around us
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 MYSTERIOUS VISION - Physiological visual illusions - mystery-play
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Did you know?
Illusions are distortions of sensory perception, "mocking" the senses so that most people are deceived

Optical illusions in the Dictionaries and Encyclopedias

An optical illusion (also called a visual illusion) is an illusion caused by the visual system and characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that does not tally with a physical measurement of the stimulus source. There are three main types: literal optical illusions that create images that are different from the objects that make them, physiological illusions that are the effects of excessive stimulation of a specific type (brightness, colour, size, position, tilt, movement), and cognitive illusions, the result of unconscious inferences. Pathological visual illusions arise from a pathological exaggeration in physiological visual perception mechanisms causing the aforementioned types of illusions.
Optical illusions are often classified into categories including the physical and the cognitive or perceptual, and contrasted with optical hallucinations.

What is an Optical Illusion? Optical Illusions can use color, light and patterns to create images that can be deceptive or misleading to our brains. The information gathered by the eye is processed by the brain, creating a perception that in reality, does not match the true image. Perception refers to the interpretation of what we take in through our eyes. Optical illusions occur because our brain is trying to interpret what we see and make sense of the world around us. Optical illusions simply trick our brains into seeing things which may or may not be real.
Try out some of these illusions and discover just how tricky it can be for your brain to accurately interpret the images from your eyes.
Optics4kids

Definition of OPTICAL ILLUSION
Something that looks different from what it is : something that you seem to see but that is not really there.
The closer building looks larger than the farther one, but it's just an optical illusion. The two buildings are actually the same size.
Learner's Dictionary

Definition of optical illusion in English:: optical illusion
Something that deceives the eye by appearing to be other than it is. An experience of seeming to see something which does not exist or is other than it appears.
OxfordDictionaries

Illusions are distortions of a sensory perception, revealing how the brain normally organizes and interprets sensory stimulation. Illusions can occur with each of the human senses, but visual illusions are the most well known and understood. The emphasis on visual illusions occurs because vision often dominates the other senses. Some illusions occur because of biological sensory structures within the human body or conditions outside of the body within one’s physical environment. Other illusions are based on general assumptions the brain makes during perception. These assumptions are made using organizational principles, such as an individual's depth perception and motion perception, and perceptual constancy that are part of our psychological ability.
Most illusions occur in people of all cultures and environmental experiences, indicating that they reflect universals in human perception. Research in illusions therefore seeks to understand how human beings perceive the environment through specific rules of perceptual construction.
llusions are also a source of fascination, commonly used by artists. In many cases two-dimensional art gains the appearance of the third dimension through the use of techniques based on principles revealed in illusions. One of the most notable uses of such principles is found in the trompe d'oeil technique. Other artists deliberately use illusion to entertain the observer by creating impossible figures. The continued development of such techniques, and the fascination they have for the viewer, reflect both the endless creativity and the appreciation for creativity that are to be found in human nature.

Understanding visual illusions
The study of illusions has focused on the visual system due to the prevalence and diversity of optical illusions. Our visual system faces a challenging task, attempting to correctly represent reality while calculating and perceiving various factors, such as light, color, texture, and size in a three-dimensional environment. Visual perception is created by our brain's interpretation of visual information and sometimes it results in fascinating visual illusions. Our mind gets "actively" involved in interpreting the perceptual input rather than passively recording the input, though it does not always accurately represent that input.
New World Encyclopedia

Glossary

Illusion - 1. A mistaken perception of reality. 2.Being deceived by a false perception or belief.
Optical illusion - 1. Of or relating to sight. 2.Relating to or using visible light
Environment - One’s physical surroundings.
Distortion - 1. A twists of fact or a misrepresentation. 2. A change in the shape of an image resulting from mistakes by our eye.
Psychologist - A person trained and educated to perform psychological research, like how the mind works and why people do the things they do.
Cornea - The transparent, convex, part of the eyeball that covers the iris and the pupil.
Transparent - Easily seen through; sheer.
Lens - A transparent, part of the eye that focuses light rays entering through the pupil to form an image on the retina.
Retina - The delicate light-sensitive part of the inner eyeball, connected to the optic nerve to the brain.
Iris - The color, round, colored part of the eye. It regulates the amount of light entering the eye.
Pupil - The black round opening in the center of the iris, through which light passes to the retina.
Optic Nerve - The nerve that goes from the retina, ling carry visual information to the brain.
Blind Spot - The small, round , region in the retina where of the optic nerve meets the eyeball. It has no rods or cones.
Traits - A important part, of a person's character.
Culture - The behavior, arts, beliefs, institutions, of a group of people
Afterimage - A visual image that stays even after the visual stimulus causing it is gone.
Background - The ground or scenery located behind something. 2. The part of a picture that appears as if it were in the distance.
Intersections - 1. A place where things intersect, especially a place where two or more roads cross. 3. Mathematics. The point where one line, surface, or solid crosses another.
Receptors - A special group of nerve endings that responds to sensory stimuli such as light.
Contrast - Two different objects. Red berries standing in contrast against the snow. 2. One thing that is different from to another. 3. The use of opposing colors, objects, or lines, next to each other to produce an strong effect in a work of art.
Camouflage - The blending in of one thing into its environment or natural surrounding. Disguise or protective coloring.
Altered - To change or make different
Superimposition - When two film clips are shown at the same time
Mirage - An optical effect that is sometimes seen at sea, in the desert, or over a hot pavement, that may have the appearance of a pool of water or a mirror in which distant objects are seen inverted. That is caused by the bending or reflection of rays of light by a layer of heated air of varying density.
Perspective - The representation of three-dimensional objects and depth relationships on a two-dimensional surface. 3. The appearance of objects in depth as see by normal vision.

 Sources of inspiration: Akiyoshi KITAOKA Julian BEEVER Michael BACH