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Saturday, September 13, 2008

11 Colorful Optical Illusions

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From classic same color illusions created by Edward H. Adelson or colors that disappear right before your eyes, to artists whose work plays with perception and “what happens outside the vantage point,” these colorful illusions will make you think twice about your perception of color. We give you 10 Colorful Illusions and explanations as to why your seeing what your seeing.

Not to be confused with the wonderful Colorful Allusion series by Prof. Oddfellow.

Classic Illusions

Same Color Illusion/ Adleson’s Checker Shadow Illusion

The 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.

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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.

“When interpreted as a 3-dimensional scene, our visual system immediately estimates a lighting vector and uses this to judge the property of the material.”

The left image below shows what appears to be a black and white checker-board with a green cylinder resting on it that casts a shadow diagonally across the middle of the board. The black and white squares are actually different shades of gray. The image has been constructed so that “white” squares in the shadow, one of which is labeled “B,” are actually the exact same gray value as “black” squares outside the shadow, one of which is labeled “A.” The two squares A and B appear very different as a result of the illusion. A second version of the same picture includes a rectangular bridge connecting square A and B to show they are the same shade of gray.
- Wikipedia

‘Just Grey’ by by Gianni A. Sarcone & Marie-Jo Waeber

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An alignment of grey bars allows us to discover the effect of color assimilation: the grey bars in contact with blue acquire a similar tone, the same for the part that touches the red color, giving the impression of color gradation. However, the grey is always grey!
- ‘Color Illusions’ by Gianni A. Sarcone & Marie-Jo Waeber

Lilac Chaser

In the first image, stare at the cross in the center and wait as the green dot erases all the purple dots leaving only the circling green.


Lilac Chaser

In this one, with no moving parts, stare at the center dot and watch as every color dissapears from your vision.

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Explanation

The lilac chaser illusion combines three simple, well-known effects:

When a visual event occurs briefly at one place in the visual field, and then a similar event occurs at an adjacent place in the same visual field, we perceive movement from the first place to the second. This is called apparent movement or beta movement, because no actual movement has occurred. Apparent movement is the basis of moving neon signs, film, and video. We see movement because such displays stimulate receptors (called Reichardt detectors) in our brains that encode movement.The visual events in lilac chaser initially are the disappearances of the lilac disks. The visual events then become the appearances of green afterimages (see next).

When a lilac stimulus that is presented to a particular region of the visual field for a long time (say 10 seconds or so) disappears, a green afterimage will appear. The afterimage lasts only a short time, and in this case is effaced by the reappearance of the lilac stimulus. The afterimage is a simple consequence of adaptation of the rods and cones of the retina. Color and brightness are encoded by the ratios of activities in three types of cones (and also the rods under mesopic conditions). The cones stimulated by lilac get “tired”. When the stimulus disappears, the tiredness of some of the cones means that the ratios evoked by the grey background are the same as if a green stimulus had been presented to these cones when they are fresh. Adaptation of rods and cones begins immediately when they are stimulated, so afterimages also start to grow. We normally do not notice them because we move our eyes about three times a second, so the image of a stimulus constantly falls on new, fresh, unadapted rods and cones. In lilac chaser, we keep our eyes still, so the afterimages grow and are revealed when the stimulus disappears.

When a blurry stimulus is presented to a region of the visual field away from where we are fixating, and we keep our eyes still, that stimulus will disappear even though it is still physically presented. This is called Troxler’s fading. It occurs because although our eyes move a little when we are fixating a point, away from that point (in peripheral vision) the movements are not large enough to shift the lilac disks to new neurons of the visual system. Their afterimages essentially cancel the original images, so that all one sees of the lilac disks is grey, except for the gap where the green afterimage appears.

These effects combine to yield the remarkable sight of a green spot running around in a circle on a grey background when only stationary, flashing lilac spots have been presented. Occasionally it seems as though the green afterimage has eaten up the lilac disks, this resemblance to Pac-Man accounting for the illusion’s alternative name.
- Lilac Chaser

Big Spanish Castle

Check out this link to see yet another great illusion that makes a black and white photo appear before your eyes in full color.

The Eclipse of Mars

Stare at the white dot in the centre of the red circle. The longer - the better (two minutes and you’ll get a much stronger effect). Always try to keep focused on the white dot. It’ll be worth it.

Soon after staring, you’ll start to see a thin rim of light around the edge. Don’t stop staring though yet! Wait another minute - keeping your head perfectly still.

Once you’ve done this, very slowly - move your head backwards - making sure to keep your eyes focused on the dot at all times. The circle’s rim will glow brilliantly with true Cyan! Keep on moving your head slowly backwards, and witness the Eclipse of Mars!…

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The blue/cyan colour chart to the right isn’t part of the illusion, but there to demonstrate that the ultra cyan you have just seen is not in the monitor’s color palette! It should be, but isn’t.

It’s an amazing effect and something I created whilst researching the problem with monitors and their inability to display real cyan. These 2 colours (red and this exact shade of cyan) work better than any other colour combination for many reasons.
- Skytopia

Illusions by Lotto Lab

Despite the fundamental differences in the apparent colour of the ‘blue’ tiles on the top of the left cube, and the ‘yellow’ tiles on the top of the right cube,…

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all the tiles are in fact physically identical (’grey’ in both cases).

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This image combines the illusions of form and colour. The centeral element of the two ‘X’ objects appear very different in color (dark blue on the left and light yellow on the right). What’s more, the angles of each ‘X’ appear either smaller or larger than 90 degrees.

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These two illusions were created by R. Beau Lotto. see more at Lotto Lab

Art

Felice Varini

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Felice Varini paints on architectural and urban spaces, such as buildings, walls and streets. The paintings are characterized by one vantage point from which the viewer can see the complete painting (usually a simple geometric shape such as circle, square, line), while from other view points the viewer will see ‘broken’ fragmented shapes. Felice argues that the work exists as a whole - with its complete shape as well as the fragments. “My concern,” he says “is what happens outside the vantage point of view.”

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“No, I am not worried about that. Everyone knows how a circle or a square looks like. My concern is what happens outside the vantage point of view. Where is the painting then? Where is the painter? The painter is obviously out of the work, and so the painting is alone and totally abstract, made of many shapes. The painting exists as a whole, with its complete shape as well as the fragments; it is not born to create specific shapes that need to satisfy the viewer. The paintings are not defined by the understanding of the viewer or what the viewer sees, but rather exist in their own right, and have their own relation to the three-dimensional space in which they were created. I work with the reality itself, with nature.”
- Interview with Poetic Mind

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Eureka Car Park Illusion

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Julian Beever

Previously mentioned here on COLOURlovers, artist Julian Beever has been creating incredible sidewalk illusions for over ten years.

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missing tiles

Now That’s Some Heavy Lifting

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sepultura

What’s inside here?

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scaramuzzino

Troll + Stool

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Pisa Leaning Tower Kicking Away

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For More Information and to see more optical illusions check out these links:

Lotto Lab : illusions of light
‘Color Illusions’ by Gianni A. Sarcone & Marie-Jo Waeber
Wikipedia: Same Color Illusion
Lilac Chaser
Skytopia
Dark Roasted Blend
Visuall Illusions

1 comment:

Optical Illusion said...

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