A visual illusion( aka optical illusion) is an illusion caused by the visual system and characterized by visually perceived images that differ from objective reality. You often run into optical illusions on a day to day life, but don’t know they have specific names. Here are some examples of visual illusions you are curious about.
1 .chromostereopsis: It is hard to focus on blue and red next to each other or reading red text on green background. Because of chromostereopsis effect.
Chromostereopsis is a visual illusion whereby the impression of depth is conveyed in two-dimensional color images, usually of red-blue or red-green colors, but can also be perceived with red-grey or blue-grey images.
2. Stroboscopic effect: The stroboscopic effect is a visual phenomenon caused by aliasing that occurs when continuous motion is represented by a series of short or speedy samples. This effect occurs in fluorescent lamps which causes moving equipment to appear stationary or moving at lower speed. Strobe lighting is commonly used stroboscopic lamps in musical concerts.
3. Zöllner illusion: This illusion is a classic optical illusion where a pattern surrounding parallel lines appear to diverge or converge when crossed by short slanted lines. It was named after German astrophysicist Johann Zöllner( two dots on “o” are known as an “umlaut mark”). This illusion is similar to three other illusion namely Hering illusion, Poggendorff illusion, and Muller-lyer illusion.
This illusion is a good example for demonstrating how lines can create visual distortion by their background.
4. Fraser spiral illusion: named after British psychologist Sir James Fraser. The illusion is also known as a false spiral. The arcs are a series of concentric circles but it appears to form a spiral.
5. Barberpole illusion: It is a visual illusion where the turning of a diagonally striped pole makes it appear as if the stripes are moving upside or downside along its vertical axis. The barber’s pole is commonly found outside barber shops.
Barberpole forces us to perceive vertical motion. This illusion occurs because a bar within an observational frame provides ambiguous information about its “real” direction of movement.
6.Ebbinghaus illusion: The Ebbinghaus illusion is an optical illusion of relative size perception. It is also known as Titchener circles.
which of the two center circle below is bigger?
7. Subjective/illusory contours: Subjective contours are visual illusions that stimulate the perception of an edge without a luminance or color change across that edge.
In above image, those spatially separate fragments give the impression of a triangle defined by a sharp illusory triangle resulting in creating an illusion. Illusory contours are mostly present in art forms of paintings.
8. Lilac chaser: It’s a visual illusion of phi phenomenon. A pac-man illusion is its alternative name.
It consists of 12 lilacs ( colors-pink, magenta, rose), blurred discs arranged in a circle (like the numbers on a clock), around a small black, central cross on a grey background. One of the discs disappears briefly (for 0.1 seconds), then the next (0.125 seconds later), and the next, and so on, in a clockwise direction. When one stares at the cross for about 5 seconds or so, one sees a gap running around the circle of lilac discs, a green disc running around the circle of lilac discs in place of the gap and the green disc running around on the grey background, with the lilac discs having disappeared in succession.
“One illusion three phenomena.”
1. theguardian.com-Ebbinghaus illusion.