Sunday, May 29, 2011

The Generals Family (Octavio Ocampo)

There are nine faces in this picture!

Missing square puzzle

From Wikipedia
The missing square puzzle is an optical illusion used in mathematicsclasses to help students reason about geometrical figures. It depicts two arrangements of shapes, each of which apparently forms a 13×5 right-angled triangle, but one of which has a 1×1 hole in it.

 Is it possible? Okay, Here's your hint...

Can you calculate the slope of the line that goes through the diagonal of the whole piece of graph paper? It's change in Y over change in X, or -13/5. Okay, what about the slope of the diagonal line that is part of the red triangle? Hmmm...that would be -8/3.

WAIT A MINUTE! Those aren't the same number! -13/5 does not equal -8/3! You know what that means, don't you? The dimensions of the red triangle aren't REALLY 8x3! And guess what! The dimensions of the blue triangle are not really 5x2!

I'll leave it to you to figure out the rest...

Is it thermometer?

Saturday, May 28, 2011

Vanishing illusion

When observers approach the image keeping their eyes on the center of the image, fireflies of blue light appear to escape. Then, some or all of them appear to extinguish (Troxler effect).

Stare Optical Illusion

Just stare at it and watch some cool things happen!

Female-Male Face Illusion

Illusion by Richard Russell of Harvard University shows two faces which are perceived as male and female. Why does our brain perceived the image on the right is a male, and the image on the left as female? What’s the difference between the images?

The difference?
Both images are off the same androgynous face. The only difference is the image on the right has a higher contrast (male), whereas the image on the left has a lower contrast (female).

Camel Shadow Illusion

At first glance you see a herd of camels walking across the desert but in actuality the camels are the little things that look like rocks and the ones you first notice are the shadows.

Vertical–Horizontal illusion

It is the tendency for observers to overestimate the length of a vertical line relative to a horizontal line of the same length

Even length and width of following tables are equal.

Size Illusions

Delboeuf illusion
The two black circles are exactly the same size; however, the one on the left seems larger

Ebbinghaus illusion
The two orange circles are exactly the same size; however, the one on the left seems smaller

Impossible objects illusion

An impossible object, it appears to have three cylindrical prongs at one end which then mysteriously transform into two rectangular prongs at the other end.
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.

Impossible object 
A variation on the 2 or 3 prong image, inspired by the work of Walter Wick, who managed to photograph his version using a partially reflective piece of glass and very careful lighting to create the illusion.

An impossible figure
  • Andreas Aronsson is a professional IT technician by day and an awesome optical illusion artist at night: 
  • He made this cleverly drawn "impossible figure" that at a glance look perfectly fine, but upon closer inspection will give your mind some sort of a Twilight Zone moment.

Necker Cube
The Necker Cube is an ambiguous line drawing
impossible cube on the right

Is the blue wall in the block or on the block? Is it the back wall or the side wall?

Rotation direction
In which direction does it spin?

Bezold effect

 The red seems lighter combined with the white, and darker combined with the black.

The two pink diagonal lines - Are they the same shade of pink or of different shades?
Look carefully, they are the same. Don't let your eyes deceive you!

Café wall illusion

First described by Richard Gregory in 1973

This optical illusion makes the parallel straight horizontal lines appear to be bent.

It is essential for the illusion that each "brick" is surrounded by a layer of "mortar" (the grey in the image). This should ideally be of a color in between the dark and light color of the "bricks".

Usage: Architecture inspired by the café wall illusion, at Melbourne Docklands

Afterimage or Ghost image

  • One of the most common afterimages is the bright glow that seems to float before one's eyes after looking into a light source for a few seconds
  • If the viewer stares at this image for 20-60 seconds and stares at a white object a negative afterimage will appear (in this case being cyan on magenta). This can also be achieved by the viewer closing his/her eyes and tilting their head up.

Kanizsa triangle

  • The Kanizsa triangle is an optical illusion first described by the Italian psychologist Gaetano Kanizsa in 1955.
  • 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.

Left-Right Brain Conflict

How many F's does the following passage contain?

Answer: Five F'S

Did you count all 6 of them or only 3?
Most people forget to include the F's located in the word "of".
Probably some people percieve f as v in rythem

"Rotating snakes"

[Click to view larger image]

Circular snakes appear to rotate 'spontaneously'.
Zack Lynch posted this fabulous optical illusion
Copyright A.Kitaoka 2003 (September 2, 2003)

"Waterways" Illusion

Scroll up this page and cut off the image with your browser window.  Warning:  This illusion is so powerful it will still trick you unless you can cut off the image accurately.
Waterways is copyrighted by Akiyoshi Kitaoka.

"Dongurakokko" Illusion

Also known as "the donguri wave" illusion
The brown leaf shapes against a green background make this look as if the entire group is flowing—making waves if you focus on the picture as a whole. 

Dongurakokko is copyrighted by Akiyoshi Kitaoka.

Friday, May 27, 2011

Moon Size Illusion (Solstice)

The full Moon beams through trees in Manchester, Maryland. Credit: June 16 , 2008 Edmund E. Kasaitis. Copyright 2008; all rights reserved

  • The Moon illusion is an optical illusion in which the Moon appears larger near the horizon than it does while higher up in the sky. 
  • This optical illusion also occurs with the sun and star constellations. 
  • It has been known since ancient times, and recorded by numerous different cultures. The explanation of this illusion is still debated

Moon Size Illusion - 2 Main Theories
1.The Ponzo Illusion

Two yellow bars are drawn across railway tracks which converge towards the distant horizon.
To the eye, the top bar appears to be wider than the bottom bar.
In the same way, with a low-lying moon the trees and houses, which are familiar foreground reference points, appear smaller against the moon, which appears bigger than it really is.
Sceptics of this theory point to airline pilots who also see the illusion, although they have no ground reference points
2.Alternate View
The brain perceives the sky as a flattened dome rather than the true hemisphere it really is.  

Maybe it's the shape of the sky. Humans perceive the sky as a flattened dome, with the zenith nearby and the horizon far away. It makes sense; birds flying overhead are closer than birds on the horizon. When the moon is near the horizon, your brain, trained by watching birds (and clouds and airplanes), miscalculates the Moon's true distance and size.

Wheels Optical Illusion

Which wheel is moving faster? or are they even moving?

A wonderful moving bicycle illusion
[Click to view large image]

Lilac chase or Phi phenomenon

  • Described by Max Wertheimer in his 1912 Experimental Studies on the Seeing of Motion
  • In this Lilac chaser illusion, the omitted space appears to be filled with a green circle when viewed long enough

On the beginning you will see 11 pink (lilac) points on a gray background. There is also a gap which moves every tenth of a second (0.1s) in the clockwise direction.
After a while, the gap will take the green color. This is due to an interesting effect in which the colors of the lilac points are inverted in the optical illusion to a green color. See the image below, that green is right opposite to pink. If the points were black, one would see white where the gaps were.

And in the end, while still focusing on the cross, the points will disapper and you will see just the grey background.
An interactive version of the illusion may be found here: 

This version allows viewers to adjust the color, saturation, and timing of the disks.

Yellow Lilac Chase Illusion:

[Click to view original illusion]

The Spinning Dancer and the Brain

  • This image, originally created by Nobuyuki Kayahara.
  • Some observers initially see the figure as spinning clockwise and some counter-clockwise.
  • The illusion derives from the lack of visual cues for depth. For instance, her arms could be swinging either in front of her to the left or behind her to the left, and hence with her circling clockwise or counter-clockwise on either her left or right foot. 
  • She changes leg because she is facing either towards or away from the observer, there being no surface features on the silhouette to indicate at any point which side of her is presented: the least ambiguous positions are her profiles when she is on either side of her circle, though it's still not known whether the foreground or background leg is on the floor, and from where she moves indeterminately either on the near or far arc across to the other profile.

See also left brain vs. right brain Test by Herald Sun

Movement illusion

An optical illusion. The two circles seem to move when the viewer's head is moving forwards and backwards while looking at the black dot.

A similar effect is in following image too.


The contrast of the object will appear darker against a black field which reflects less light compared to a white field even though the object itself did not change in color

The horizontal grey bar is the same shade throughout

Ponzo Optical Illusion

  • In the Ponzo illusion the converging parallel lines tell the brain that the image higher in the visual field is farther away therefore the brain perceives the image to be larger
  • In fact, the two images hitting the retina are the same size

USAGE: The three red lines are duplicates, they are the exact same size.

And Muller-Lyer Ticket Window

What can you see?

Can you see both the frog and the horse on this visual illusion?

Duck-Rabbit illusion

The Division Bell (Real usage)

  • The album cover artwork for Pink Floyd's The Division Bell is an example of a Rubin-vase-like construction. 
  • The two metal heads in profile facing each other form the image of a third face looking directly at the viewer.

Rubin vase

A famous set of cognitive optical illusions developed around 1915 by the Danish psychologist Edgar Rubin.