The term optical illusion refers to any illusion that deceives the human visual system into perceiving something that is not present or incorrectly perceiving what is present. There are physiological illusions and cognitive illusions.

Optical illusions can occur naturally or be demonstrated by specific visual tricks that show particular assumptions in the human perceptual system.

A mirage is an example of a natural illusion. The variation in the apparent distance of the Moon is another natural illusion. These are both examples of natural optical phenomena.

Developed or discovered illusions includes phenomena such as the Necker cube and the Hermann grid. Understanding these phenomena is useful in order to understand the limitations of the human visual system.

Physiological illusions, such as the afterimages following bright lights or adapting stimuli of prolonged alternating patterns (contingent perceptual after-effect, CAE), are the effects on the eyes of prolonged stimulation of a specific type - brightness, tilt, colour, movement and so on. The theory is that stimuli have individual dedicated neural paths in the visual cortex for the early stages of visual processing, repetitive stimulation of only a few channels misleads the visual system.

Cognitive illusions are more interesting and well-known. Instead of demonstrating a physiological base they interact with different levels of perceptual processing, in-built assumptions or 'knowledge' are misdirected. Cognitive illusions are commonly divided into ambiguous illusions, distorting illusions, paradox illusions or fiction illusions. They often exploit the predictive hypotheses of early visual processing.

Ambiguous illusions are pictures or objects that offer significant changes in appearance. Perception will 'switch' between the alternates as they are considered in turn as available data does not confirm a single view. The Necker cube is a well known example, the motion parallax due to movement is being misinterpreted, even in the face of other sensory data.

Distorting illusions are the most common, these illusions offer distortions of size, length or curvature. They were simple to discover and are easily repeatable. Many are physiological illusions, such as the Cafe wall illusion which exploits the early visual system encoding for edges. Other distortions, such as coverging line illusions, are more difficult to place as physiological or cognitive as the depth-cue challenges they offer are not easily placed. All pictures that have perspective cues are in effect illusions. Visual judgements as to size are controlled by perspective or other depth-cues and can easily be wrongly set.

Paradox illusions offer objects that are impossible or paradoxical, such as the Penrose triangle or impossible staircase seen, for example, in the work of M. C. Escher. The triangle is a illusion dependent on a cognitive misunderstanding that adjacent edges must join. They occur as a byproduct of perceptual learning.

Fiction illusions are the perception of objects that are genuinely not there to all but a single observer, such as those induced by schizophrenia or hallucinogenic drugs.

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If you’re thinking about getting a tattoo, here’s something you should know. Scary animals with subtle drop-shadows look much better than those without shadows. Above, you will see the original image, that this man has tattooed. Very cool, especially how the tail of the scary arachnid looks like it’s in the air and about to strike.

Next, look at the image below and you’ll see no drop shadow. Now it just looks like a puny drawing on his arm.

Labels: Illusion Tips, New Illusions

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Previously i had posted about How Rainbows Are Made?Now here is the tip to make your own Rainbow.
Fill a glass of water (almost to the top) and place it at the very edge of the counter in a dark kitchen. Place a sheet of plain white paper on the floor a few inches away from the counter. Put two pieces of masking tape over the front of a flashlight so that the light comes out of a slit about 1/8 inch (0.3 cm) wide. Shine this light across and down into the water as shown in the figure. When a narrow beam of light is passed through a glass of water, a spectrum can be seen on a white sheet of paper.

Can you see a small rainbow on the white paper? If not, move the flashlight around a little until you achieve the best results.

Now that you know what to look for, you will begin to notice small rainbows wherever sunlight falls on water, glass, or plastic that has a tapered shape. Look for rainbows produced by the beveled edge of a mirror or a chandelier.


-Dr. Kurt Nassau's book

Labels: Illusion Tips, Natural illusions, New Illusions

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This is an amazing illusion trick with mathematics.You can play this trick with anybody.

Just try it friends, you will be amazed.Please comment what you think about this post.


It goes like this:

Think of a number between 1 and 10 .

Now double it.

Now add 8 to that. You have new number.

Take your new number, and divide it by 2. You have a new number once again.

Now, I want you to subtract your original number from the number you have now. Concentrate on this number.

Let’s switch gears. I want you to think of the letter in the alphabet that corresponds with your number. That is, if your number is 2, think of B. If your number is 3, think of C. And so on.

Concentrate on that letter. Got it? OK, now, think of a country that begins with that letter. Can be anywhere. Got it? Great. Now concentrate on your country.

With your country in your mind, let’s go to the next letter in the alphabet. So, if your country begins with B, go to letter C. And so on.

You’re now thinking of your country and your other letter. Now, think of an animal that begins with that other letter. Got your animal? Good. Now concentrate and visualize the color of that animal. Got it? Good. Now concentrate on three things: your country, your animal, and the color of the animal. Try to see it in your mind.

Just remember that there are no grey elephants in Denmark.

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Just before some days i posted Christopher Walken in Space Illusion in which Christopher Walken appears to floating through space.

Now you can make your own illusions too....

Here is the Trick to make your own animated illusions.

>Simple Guide To Make An Animated Illusion.

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These guys are really going an amazing trick.

Labels: DoItYourself Illusions, Illusion Tips, Outdoors Illusions, Perspective Illusion

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Well you may have seen this impossible triangle before,but you can learn how to make this now by Scott Henderson's(illusion artist and magician) trick.
This picture has not been edited,yet it appears to be an impossible triangle!



This photo has not been edited one bit. This is a picture of the penrose impossible triangle that is sitting in front of the desk. If we look at it from the right angle, it appears exactly as it does in the picture above. Many people think it can't be done. But it is actually possible! And now, you can build your own "impossible triangle" in less than 5 minutes!



Make your own Impossible Triangle learn here....

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