Optical Illusion

• Optical illusion
There is an effect of visual perception, when the observer, consciously or involuntarily, gives an explanation of the picture he is observing that does not correspond to reality. He is well known to everyone who has observed clouds running across the sky, sometimes taking the form of well-known visual objects. The same effect can take place when observing the pattern of distribution of shadows of three-dimensional objects at some of their angles in relation to light sources.

• Illusions of color perception
It has been known for about a hundred years that when an image consisting of light and dark areas appears on the retina of the eye, the light from the brightly lit areas seems to flow into the dark areas. This phenomenon is called optical irradiation.

• One of such illusions was described in 1995 by MIT professor Edward Adelson ("the illusion of Adelson's shadow"). He drew attention to the fact that the perception of color significantly depends on the background and the same colors on different backgrounds are perceived by us as different, even if they are close and visible to us at the same time.

• Depth perception
The illusion of depth perception is an inadequate reflection of the perceived object and its properties. Currently, the most studied are the illusory effects observed in the visual perception of two-dimensional contour images. The brain unconsciously sees only one-convex (one-curved) drawings. Perception depends on the direction of external (real or implied) lighting.

• Perception of size
Illusions often lead to completely incorrect quantitative estimates of real geometrical values. It turns out that you can be mistaken by 25% or more if eye estimates are not checked with a ruler.

• Eye-size estimates of geometrical real values ​​very strongly depend on the nature of the background of the image. This applies to lengths (Ponzo illusion), areas, radii of curvature. It can also be shown that what has been said is also true for angles, shapes, and so on.

• shifters
A shape-shifter is a type of optical illusion in which the nature of the perceived object depends on the direction of the gaze. One of these illusions is the "duck-hare": the image can be interpreted both as an image of a duck and as an image of a hare.

• Stereo illusions
Periodic texture defects create the illusion of volume in the same way as a regular stereo pair. Due to the periodicity, a false visual combination of adjacent repeating elements into one is possible in case of a violation of normal coordination between the convergence of the eyes and the accommodation of the lenses. In this case, the drawing seems to be located closer or further than the true distance from the observer, and deliberately added defects are perceived as volumetric elements.
The method allows you to combine both parts of a stereopair in one image, removing restrictions on their size, however, it imposes some restrictions on the content of figures and is practically calculated using computers.

• Tilted tower illusion
When looking at two identical pictures, side by side and distorted by perspective, you may get the impression that they were taken from different angles. This effect was described in 2007, and is called the leaning tower illusion, as it was shown in the example of the Leaning Tower of Pisa. In 2007, this effect won first place in the Best Illusion of the Year competition.

• Moving illusions
The effect is enhanced by tilting, rotating, moving the head closer / away
Still image appears to be moving
When looking at the same moving balls, you can see that they are of different sizes.
The same animation can depict a rotating object clockwise, counterclockwise, or alternately (oscillate).