I don't believe my eyes!

[Fit of Rage]

Originally posted by Troll King
An easier explanation for the triangle one is that people expect the shapes to form a perfect triangle, when in fact neither shape is a triangle. Because of the slight variation in the slopes of the red and green triangles, rearranging the shapes will give you two distinct shapes with the same area. We only expect the two shapes to be the same triangle, when in fact, that wouldn't be possible.

Exactly TK. It's all in the pixel placement on the screen. But the change in slope is so subtle that most people don't notice unless they print it out and check with a ruler or something.

[Troll King]

No ruler needed. Just count the grid markers.

[Vitron2]

Without checking the markers on the triangles it is hard to detect the curvature. But that is the point of the optical illusion.


Vitron

[ÆNIMA]

Excuse my double post...this one's an answer to the original post, the 2nd..is more optical illusions.

The answer, provided by: http://www-bcs.mit.edu/people/adelso..._illusion.html

The visual system needs to determine the color of objects in the world. In this case the problem is to determine the gray shade of the checks on the floor. Just measuring the light coming from a surface (the luminance) is not enough: a cast shadow will dim a surface, so that a white surface in shadow may be reflecting less light than a black surface in full light. The visual system uses several tricks to determine where the shadows are and how to compensate for them, in order to determine the shade of gray "paint" that belongs to the surface.

The first trick is based on local contrast. In shadow or not, a check that is lighter than its neighboring checks is probably lighter than average, and vice versa. In the figure, the light check in shadow is surrounded by darker checks. Thus, even though the check is physically dark, it is light when compared to its neighbors. The dark checks outside the shadow, conversely, are surrounded by lighter checks, so they look dark by comparison.

A second trick is based on the fact that shadows often have soft edges, while paint boundaries (like the checks) often have sharp edges. The visual system tends to ignore gradual changes in light level, so that it can determine the color of the surfaces without being misled by shadows. In this figure, the shadow looks like a shadow, both because it is fuzzy and because the shadow casting object is visible.

The "paintness" of the checks is aided by the form of the "X-junctions" formed by 4 abutting checks. This type of junction is usually a signal that all the edges should be interpreted as changes in surface color rather than in terms of shadows or lighting.

As with many so-called illusions, this effect really demonstrates the success rather than the failure of the visual system. The visual system is not very good at being a physical light meter, but that is not its purpose. The important task is to break the image information down into meaningful components, and thereby perceive the nature of the objects in view

[ÆNIMA]

This site's just tight: http://www.liquidgeneration.com/sabo...l_sabotage.asp

Go all the way to the end of the little dealy, you'll love it.

My personal favorite (Count the black dots):

The explanation by http://www.yorku.ca/eye/hermann1.htm

To understand the receptive field explanation for the Hermann grid illusion requires a basic understanding of receptive fields.
Once again, it is a matter of lateral inhibition between the center and surround of the receptive field. Note the lower right part of the diagram. The receptive field that lies at the intersection of the white cross has more light falling on its inhibitory surround than does the receptive field that lies between the two black squares. Consequently, the excitatory center of this receptive field between the squares yields a stronger response than that which lies at the intersection of the white cross. This explanation is appropriate for those circumstances where the receptive fields are larger than the spaces between the squares.

Receptive fields in the central fovea are much smaller than in the rest of the retina. This is represented in the upper right of the diagram. In the Hermann grid you probably did not see a dark area when you looked directly at the intersection of the white cross, but did see dark areas in your peripheral vision. To prove to yourself that this is not some trick, just get up and walk away from your computer screen. When you are at some distance from it, you will undoubtedly notice that the dark blob is visible even at your fixation point. I leave it to you to figure out why this happens.



One last great site: http://onkar.s5.com/illusions/

[Ralex]

WoW.

[Troll King]

Woo! My alma mater's useful for a change

[Scout1]

Originally posted by ÆNIMA
This site's just tight: http://www.liquidgeneration.com/sabo...l_sabotage.asp

Go all the way to the end of the little dealy, you'll love it.

omfg thats not cool man O_O

[Mayo Inc.]

we learned about optical illusions in psych last year... the ones where you stare at things and see outlines like the jesus one is a result of chemicals in your eye burning away or something

[Material Girl]

And oh how they burn.

[ÆNIMA]

I had that in psych class too, although I understood it that it's your rods and cones reacting, and the reaction just stays there for a while. Or if you stare at a single color a lot, the image I guess could burn in sort of..but the brain tries to save it by projecting the opposite color...or something:P


MG, is that avatar from digitalblasphemy.com if not..where? it's purdy

[Luis Logic]

1st post..eh ><

[Xog]

ew it wont let me put the pic up.. heres the link
http://sheikhnabeel.8m.com/cgi-bin/i/Slide5.jpg



^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ my favorite

[Mr. Peanuts]

saw that top one 3 years ago.

[Mennoowh]

i really love this one: