Home InfoPhotos Optical Illusions.

Optical Illusions.

by Anastasia
Career choices for students, unemployed, underemployed

An optical illusion which is also called a visual illusion can be described as perception of the images differently than they actually are. Our eyes see something, pass this info to the brain, and because of the different reasons and factors our brain makes us think that we see something different. Since I’m not a doctor myself and can’t write scientific explanations (though I do understand how it works) I use the material explaining the origin of illusions from Wikipedia.

Most of the illusions were discovered by psychologists and later people started using these effects to create new illusions. There are basically several main effects on a human eye and brain and multiple variations of the visual presentation of these effects. You might have seen multiple optical illusions online but we’d like to go just a bit deeper into it and show you the basics. Also, today we won’t speak about illusions where on once pic you can see multiple faces or should find say 10 people as these are more work of art of the painter than the illusion.

Basically there are 3 main type of optical illusions: literal optical illusions that create images different from the objects that make them, physiological illusions that we see as the result of eyes excessive stimulation of a specific type (brightness, tilt, color, movement), and cognitive illusions where the eye and brain make unconscious inferences.

Physiological illusions

We see this type of illusion as the effect on the eyes or brain of excessive stimulation of a specific type, such as brightness, tilt, color, movement etc. The most usual and well-known demonstration of these effects are the afterimages following bright lights or when you stare at some moving or still image for long and see other things move after that or when the image starts moving on its own. The theory is that stimuli have individual dedicated neural paths in the early stages of visual processing, and that repetitive stimulation of one or a few channels causes a physiological imbalance that alters perception.

Here are some pretty popular examples of illusions of this type.

Lilac chaser

Lilac chaser consists of 12 lilac blurred disks arranged in a circle around a small black, central cross on a gray background. One of the disks disappears briefly (for about 0.1 second), then the next (about 0.125 second later), and the next, and so on, in a clockwise direction. When one stares at the cross for about 20 seconds or so, one first sees a gap running around the circle of lilac disks, then a green disk running around the circle of lilac disks, then a green disk running around on the gray background, with the lilac disks having disappeared or having been erased by the green disk. This is due to an interesting effect in which the colors of the lilac disks are inverted in the optical illusion to a green color.

lilac

Peripheral drift illusion

The center of the image seems to be moving from left to right and top to bottom, when you move your eyes just a bit to a side from the center. The peripheral drift illusion refers to a motion illusion generated by the presentation of a sawtooth luminance grating in the visual periphery.

drift

The red, white and blue flag.

Stare at the center of the weird flag for about 1 minute. Don’t move your eyes. Then look at an empty white sheet of paper, and you’ll see the red, white, and blue flag. This is an afterimage or ghost image, an optical illusion that refers to an image continuing to appear in one’s vision after exposure to the original image has ceased. If the viewer stares at the image for 20-60 seconds and stares at a white object, a negative afterimage will appear.

us_flag

Black and Grey

Stare at the black dot… after a while, the gray haze around it will appear to shrink.

black_gray1

Hermann grid

This illusion is characterized by “ghostlike” gray blobs perceived at the intersections of a white (or light-colored) grid on a black background. The gray blobs disappear when looking directly at an intersection.

herman1

Jesus Christ

This illusion is pretty popular and a really great example of the afterimage effect.

jesus

Che Guevara

che_guevara

Color Dove illusion

In this effect, an empty (white) shape is presented on a colored background for several seconds. When the background color disappears (becomes white) an illusionary color, similar to the original background is perceived within the shape.

dove1

Bezold effect

The red seems lighter combined with the white, and darker combined with the black. Same about the rest of the colors when you see them on white and black. These color shades influence the way you see the other colors.

bezold1

Cornsweet illusion

Left part of the picture seems to be darker than the right one. In fact they have the same brightness. We can see this effect because of the small gradient effect in the middle of the image.

cornsweet

Fraser spiral 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.

fraser_spiral

Short-Circuit Your Brain

Look at the chart above and say the COLOR of the word, not the word itself. With this illusion you can see how’s your brain working. One part of it tries to read and the second one sees the color.

brain

Cognitive illusions

Cognitive illusions are assumed to arise by interaction with assumptions about the world, leading to “unconscious inferences,” an idea first suggested in the 19th century by Hermann Helmholtz. Cognitive illusions are commonly divided into ambiguous illusions, distorting illusions, paradox illusions, or fiction illusions.

1. Ambiguous illusions

Ambiguous illusions are pictures or objects that elicit a perceptual ‘switch’ between the alternative interpretations.

The Necker cube

The Necker Cube is a ambiguous line drawing. It is a wire-frame drawing of a cube in isometric perspective, which means that parallel edges of the cube are drawn as parallel lines in the picture. When two lines cross, the picture does not show which is in front and which is behind. This makes the picture ambiguous; it can be interpreted in two different ways. When a person stares at the picture, it will often seem to flip back and forth between the two valid interpretations (so-called multistable perception).

necker_cube

Isometric illusion.

The shape can be perceived as either an inside or an outside corner. In general, any shape built entirely of the same-length (i.e., isometric) lines that does not clearly indicate relative direction between its components will evoke such a perceptual “flip-flopping”.

book1

Reversing Staircase

Stare at the Reversing Staircase Illusion until it changes to a different staircase.

reversing

Spinning Dancer

If the foot touching the ground is perceived to be the left foot, the dancer appears to be spinning clockwise (if seen from above); if it is taken to be the right foot, then she appears to be spinning counterclockwise.

dancer

2. Distorting illusions

Distorting illusions are characterized by distortions of size, length, or curvature. Below you will find some nice examples.

Café wall illusion

This optical illusion makes the parallel straight horizontal lines appear to be bent. To construct the illusion, alternating light and dark “bricks” are laid in staggered rows. It is essential for the illusion that each “brick” is surrounded by a color between the dark and light color of the “bricks”.

cafe

Müller-Lyer illusion

The Müller-Lyer illusion consists of nothing more than an arrow. When viewers are asked to place a mark on the figure at the mid-point, they invariably place it more towards the “tail” end. Another variation consists of two arrow-like figures, one with both ends pointing in, and the other with both ends pointing out. When asked to judge the lengths of the two lines, which are equal, viewers will typically claim that the line with inward pointing arrows is longer. One possible explanation is that one sees the lines as three-dimensional, such as the outgoing and ingoing corners of a room. Another possible explanation is that the line with arrows pointing inwards may simply appear longer because the arrows themselves extend past the line.

muller1

Ebbinghaus illusion

The two orange circles are exactly the same size; however, the one on the left seems smaller. We see the size differently because of the size of the objects around and the distance from them to the orange circles.

flower1

Ehrenstein illusion

The sides of a square placed inside a pattern of concentric circles take an apparent curved shape.

ehrenstein

Hering illusion

The two vertical lines are both straight, but they look as if they are bowing outwards. The distortion is produced by the lined pattern on the background, that simulates a perspective design, and creates a false impression of depth.

hering

Jastrow illusion

The two figures are identical, although the lower one appears to be larger.

jastrow

Kanizsa triangle

In the accompanying figure a white equilateral triangle is perceived, but in fact none is drawn. This effect is known as a subjective or illusory contour. Also, the nonexistent white triangle appears to be brighter than the surrounding area, but in fact it has the same brightness as the background.

kanizsa

Leaning tower illusion

The Leaning Tower Illusion is an optical illusion that presents two identical images of the Leaning Tower of Pisa side by side. Although the images are identical, we have the impression that the tower on the right leans more, as if photographed from a different angle.

tower1

Illusory motion

The term illusory motion, also known as motion illusion, is used to define the appearance of movement in a static image. This is an optical illusion in which a static image appears to be moving due to the cognitive effects of interacting color contrasts and shape position.

illusory_motion

Poggendorff illusion

A straight black and red line is obscured by a grey rectangle. The blue line, rather than the red line, appears to be a continuation of the black one, which is clearly shown not to be the case on the second picture.

poggen

Same color illusion

The squares A and B on the illusion are the same color (or shade), although they seem to be different. This can be proven by copying the image into an art program and sampling the color of A and then of B, which will show that they are in fact the same color.

same_color_1

same_color_2

Zöllner illusion
In this figure the black lines seem to be unparallel, but in reality they are parallel. The shorter lines are on an angle to the longer lines. This angle helps to create the impression that one end of the longer lines is nearer to us than the other end. This is very similar to the way the Wundt illusion appears. It may be that the Zöllner illusion is caused by this impression of depth.

zollner

3. Paradox illusions

Paradox illusions are generated by objects that are paradoxical or impossible, such as the Penrose triangle or impossible staircases seen, for example, in M. C. Escher’s Ascending and Descending and Waterfall. The triangle is an illusion dependent on a cognitive misunderstanding that adjacent edges must join.

Penrose triangle

The tribar appears to be a solid object, made of three straight beams of square cross-section which meet pairwise at right angles at the vertices of the triangle they form.

penrose_triangle

penrose

Blivet

This blivet portrays two irreconcilable perspectives at once, creating a “lost” layer between the top two rods, and an impossible extra, vanishing rod in between the bottom two.

blivet

Impossible staircases

imp_stairs2

Ascending and Descending and Waterfall illusions

waterfall1

4. Fictional illusions

Fictional illusions are defined as the perception of objects that are genuinely not there to all but a single observer, such as those induced by schizophrenia or a hallucinogen. These are more properly called hallucinations.

Here’s an amazing website where you can see multiple illusions including some great animated illusions www.michaelbach.de. You will also find explanations to many effects so be sure to visit it if you’re interested in optical illusions.

Related Posts

24 comments

Shapes Vanish Before Your Eyes Illusion! | Insane Optical Illusions May 24, 2009 - 10:12 pm

[…] Optical Illusions. […]

Reply
The Spinning Dancer Illusion | Insane Optical Illusions May 24, 2009 - 11:41 pm

[…] Optical Illusions. […]

Reply
| Insane Optical Illusions May 26, 2009 - 12:01 am

[…] Optical Illusions. […]

Reply
Drake Bradley June 14, 2009 - 9:28 pm

The Lilac Chaser and the Same Color Illusion are really amazing. Lilac Chaser shows the effects of apparent motion, negative afterimages (when the “moving” disk turns green), and perceptual fragmentation or fade (when the lilac disks disappear). The Same Color Illusion shows one of the most striking examples of brightness contrast I have ever seen. Square A is surrounded by more white than square B, so contrast would make it appear darker. But that is only part of the story!

Square B’s lighter appearance is augmented by a Helmholtzian scaling of apparent lightness (R) based on the perceived incident illumination (E). The subjectively lighter square B appears to be in the shade of a cylinder, and yet it has the same luminance value (L) as square A — this is, after all, why this is an illusion. B’s judged reflectance (lightness) must therefore be higher than A since it manages to sent the same absolute amount of light to the eye as square A even though it receives less incident light. In algebraic terms, R = L/E (i.e., perceived lightness = luminance / perceived illuminance). Because E (illuminance) is perceived to be less for square B, but its physical luminance (L) is the same as A, the value of R for B will be scaled upward. In a galaxy far, far away, I made a similar argument by way of explaining an illusion of lightness in the subjective Necker cube…

Reply
Rameeshay June 15, 2009 - 10:45 pm

Wow!!!! These optical illusions are soo cool. Thanx for showing me how to make the Cafe Wall illusion. Thanks. =)

Reply
Understanding Human Eyes Vision and Color Image Processing | VISION CORRECTION CALIFORNIA June 20, 2009 - 1:38 am

[…] Optical IllusionsThere are basically several main effects on a human eye and brain and multiple variations of the visual presentation of these effects. […]

Reply
Dhinakar October 3, 2009 - 5:51 am

Hey its amazing man!!!!!!!!!!1
Welldone…

Reply
kream47 November 2, 2009 - 5:01 pm

the blivit one… that got me confused

Reply
Mickey November 30, 2009 - 10:41 pm

Most of these optical illuisons, don’t make sense to other people. The Dancer one was my favorite, but my question about it is “is it really moving?”. But again i find that this website needs way more optical illusions. None of those one’s where you see a sprial right in the center of the picture. I would really like to download my own on here. Again I love this website, BUT it does need a lot more stuff on it instead of those cheesy ones.Thanks a lot! Bye. 🙂

Reply
Anne March 24, 2010 - 1:46 pm

WOW! What a great array of illusions. I came across your site while looking for another. Couldn’t remember what it was called at that moment but it’s an Optical Illusion gift. One of the best I have ever seen. Anywho…this is an optical illusion post so why not another linky?

http://www.turnyourhead.com
Reminds me of the old vase/face illusions.

Reply
stupid October 2, 2010 - 5:49 pm

i so totally agree with u its awsome theumbs up for optical illusions

Reply
MOSSY February 3, 2012 - 7:32 am

WELL DONE WITH THE THUMBS!!!

Reply
Raiderdline61 March 24, 2010 - 4:31 pm

Amazing!!!! 😀 It was awesome!!! especially the flag one! I tried to draw the waterfall one for my art project, but I couldn’t really draw it properly :(. But these illusions are awesome!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Reply
me June 11, 2010 - 12:26 pm

this is ritartrd and so am i because

Reply
CONNOR June 15, 2010 - 4:26 am

COOOOOOOOL :D.

Reply
robert pattinsion July 27, 2010 - 9:12 am

this were awesome i mean to say incredible just they befool your eyes so easily

Reply
Anne August 10, 2010 - 4:14 am

nice one! hahahahahahaha…my eyes tricked me!

Reply
stupid October 2, 2010 - 5:46 pm

its stinking awsome its amazing but stupid at the same time who found these things out nerds?

Reply
Sheemers November 11, 2010 - 9:23 pm

Why can’t I find a better explanation for literal optical illusions anywhere? what are they? what’s an example of one?

Reply
Sabrina March 27, 2011 - 12:43 pm

First of all they can be nerds but at least they’re not dumb like u stupid.

Reply
korbin despain May 3, 2011 - 1:37 pm

this is gay

Reply
jOHN August 6, 2011 - 8:30 am

Owh.. Nice one (: Can I use that for my report? haha:) Thanks!! You’re so gooood!! =>

Reply
manasi November 24, 2011 - 7:51 am

very nice
very interesting

Reply
Mohammed Haneef October 18, 2012 - 2:46 am

Very Very Nice

Reply

Leave a Comment

This website uses cookies to improve your experience. We'll assume you're okay with this, but you can opt-out if you wish. Accept Read More