Optical Illusion

An optical illusion (also called a visual
illusion) is characterized by visualll
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.
three main types
Optical Illusion

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1. literal optical illusions that create images
that are different from the objects that make
them,
2. physiological ones that are the effects on
the eyes and brain of excessive stimulation
of a specific type (brightness, tilt, color,
movement), and
3. cognitive illusions where the eye and brain
make unconscious inferences. They can also
be known as "mind games".
Hermann grid illusion

characterised by
"ghostlike" grey
blobs perceived at
the intersections of
a white (or lightcolored) grid on a
black background.
The grey blobs
disappear when
looking directly at
an intersection.
Grid Illusion

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 illusion and the
Scintillating grid illusion.
A scintillating grid illusion
discovered by E. Lingelbach in 1994

A scintillating grid
illusion. Shape,
position, colour,
and 3D contrast
converge to
produce the
illusion of black
dots at the
intersections.
Same color illusion

also known as Adelson's checker shadow
illusion, checker shadow illusion and
checker shadow—is an optical illusion
published by Edward H. Adelson, Professor
of Vision Science at MIT in 1995. 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 sampling
the colors of A and B in an image-editing
program. By erasing everything except the
two labeled squares, the illusion is dispelled.
Same color illusion
Afterimage

an optical illusion that refers to an image
continuing to appear in one's vision after the
exposure to the original image has ceased.
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. The phenomenon of afterimages
may be closely related to persistence of
vision, which allows a rapid series of pictures
to portray motion, which is the basis of
animation and cinema.
Motion aftereffect
http://upload.wikimedia.org/wikipedia/en/2/28
/Illusion_movie.ogg
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.
Ambiguous illusions

are pictures or objects that elicit a
perceptual 'switch' between the
alternative interpretations. The Necker
cube is a well known example; another
instance is the Rubin vase.
Construction

The distinction is exploited by devising an
ambiguous picture, whose contours match
seamlessly the contours of another picture
(sometimes the same picture; a practice M.
C. Escher used on occasion) or more often
another picture. The picture should be "flat"
and have little (if any) texture to it. The
stereotypical example has a vase in the
center, and a face matching its contour
(since it is symmetrical, there is a matching
face on the other side).
Ambiguous illusions
Rubin’s Vase/Face
The Division Bell by Pink Floyd
Transformation
Distorting illusions

are characterized by
distortions of size,
length, or curvature.
A striking example
is the Café wall
illusion. Another
example is the
famous Müller-Lyer
illusion.
Paradox illusions
http://www.scientificpsychic.com/graphics/

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.
Maurits Cornelis Escher
(17 June 1898 – 27 March 1972)

a Dutch graphic
artist. He is known
for his often
mathematically
inspired woodcuts,
lithographs, and
mezzotints. These
feature impossible
constructions,
explorations of
infinity, architecture,
Penrose triangle

The triangle is an
illusion dependent
on a cognitive
misunderstanding
that adjacent edges
must join.
The Penrose triangle

also known as the Penrose tribar, is an
impossible object. It was first created by
the Swedish artist Oscar Reutersvärd in
1934. The mathematician Roger Penrose
independently devised and popularized it in
the 1950s, describing it as "impossibility in
its purest form". It is featured prominently in
the works of artist M. C. Escher, whose
earlier depictions of impossible objects
partly inspired it.
The three hares

is a circular motif
which appears in
sacred sites from
the Middle and Far
East to the churches
of south west
England (where it is
often referred to as
the "Tinners’
Rabbits").
Fictional illusions

defined as the perception of objects that are
genuinely not there to all but a single
observer, such as those induced by
schizo’phrenia or a ha’llucinogen. These
are more properly called hallucinations.
Multi-Stability vs.
Uncertainty Principle 267-272

In quantum mechanics,
the Heisenberg
uncertainty principle
states by precise
inequalities that certain
pairs of physical
properties, such as
position and
momentum, cannot be
simultaneously known
to arbitrarily high
precision.

That is, the more
precisely one
property is
measured, the less
precisely the other
can be measured.
Visual Clues & Perspective
Most optical Illusions
depend on the
techniques and
conventions of drawing.
The illusion is that
you are seeing a 3
dimensional object,
but you are looking
at a 2 dimensional
construction.
ALWAYS ASK: HOW
WAS THIS PICTURE
MADE?
How many legs?
Monkey King’s Eyes
Penetrating Insight
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火眼金睛
【huǒyǎnjīnjīng】
piercing eye;
penetrating insight
main character in
the classical
Chinese epic novel
Journey to the West
(西遊記).