Illusions

1
Illusions

• By Linda Doan

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The Hermann Square

• Do you see gray circles in the intersection
  of the squares? Look again, do those circles
  really exist?

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The Hermann Squares Explanation

• Explanation 2
• Our eyes respond to a variety of light sources
  ranging from dark to light. Since there are more
  black than white, the eyes try to adjust to the
  dark level causing the white to look gray.

• Explanation 1
• PROXIMITY IMAGE
• The dark squares are so close together and the
  eyes are used to seeing things closed up.
  Because the square are slightly apart, the eyes
  make the image as if they are together.

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Explanation to the Hermann Square Taken Online

• This is caused by a phenomona called "the centre
  surround analysis."This is due to a physiological
  mechanism called lateral inhibition. Your eye has
  two sets of receptors in the eye (called
  ganglions), one set in the centre and the other
  surrounding it. When the central one is
  stimulated the signal is sent straight though to
  the brain. But when the surrounding ones are
  stimulated, they also send a signal to the brain,
  but at the same time inhibit the central
  ones.Thus when looking at the grid, and focusing
  on one paticular point, the amount of inhibition
  varies depending on the quantity of "alternative"
  stimulation around that point. Thus the
  crossroads have black spots, due to the 4
  adjacent squares. The amount of inhibition is
  enough for the brain to be into blotting out the
  crossroads with a grey spot. The other area's of
  the grid stay white, because the inhibition is
  not sufficient for the brain to black them out.It
  also works for coloured grids, with a similar
  effect, other than the spot changes colour
  depending on the 2 grid colours (eg blue spots in
  a green/yellow grid). This shows that it works
  for cone cells as well as rod cells.
• From Why does the Ilusions arise?
  http//wwwusers.york.ac.uk/hwf100/
  illusions/page4.html 2002.

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Rotating Circles

• Stare into the red dot in the circle and slowly
  move towards the screen. What do you see? The
  rings on the outside are moving in different
  directions right? Are they really moving?

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Rotating Circles Explanation

• The reason why you re seeing this is because the
  eyes are used to seeing motions and to perceive
  things. Because you are staring at a certain
  angle and moving away the computer, the eye
  assume that it is moving. The rings seem rotate
  different directions because the shape of each
  ring appears to go different directions. In other
  words, the eye interpretes visual indication to
  assist in day to day living. In this case, the
  visual indication mislead one to perceive motion.

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Two Shades of Green

• Look at the two shades of green. They appear to
  be different shades of green. Are they really?

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Two Shades of Greens Explanation

• Dithering
• A technique of creating a new colors where the
  colors are printed so close together that they
  mix to create a new color. Dithering is used
  primarily for color printing. If you look very
  closely at a magazine picture, you will see how
  the full-color pictures are actually made from
  thousands of small dots using this color
  dithering process

• The two shades of green that you were looking at
  were really just one shade of green. The reason
  why you see a darker green is because of the dark
  color next to it. The dark colors combine
  together to give you the dark shade of green.
  The same with the light shade. This technique is
  called dithering.

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Tree Work of Art

• Look closely at the picture and tell me what you
  see? Is it a tree or heads of people?

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Tree Work of Arts Explanation

• Figure ground
• This is when you see different images when you
  take different objects on the painting as the
  background.
• For example a picture of a vase. If you take
  the vase as the background, you will see two
  faces, while if you take the faces as the
  background you will see the vase.

• When you are just glancing at this picture, you
  might just see a tree. But if you look at it
  deeply and take the different object for the
  background, you might notice a difference. If
  you take the white as the background, you will
  see a tree. But if you take the
• trunk of the background as the background, you
  will see different heads.

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A Bird In The Bush

• What is this sign saying? A BIRD IN THE BUSH?
  Look again.

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A Bird In The Bushs Explanation

• There are two thes. The reason youre seeing that
  is because your brain assume things. All these
  years that you have been reading, there are
  rarely any sentence that includes two thes side
  by side. Your eyes read the sign and tends to
  skip the word that does not seem right.

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Blind Spot

• Look at the X with your left eye closed. Move
  slowly towards or away from the screen. At a
  certain distance from the screen, you will notice
  the O to disappear. Why?

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Blind Spots Explanation

• Although our eyesight seems complete in each eye,
  there is actually a large "hole" or blindspot
  created by the spot in the retina where the
  nerves exit the eye. Therefore, as you move back
  and forth, the O will be in the blind spot where
  you will not see the O.