Optical illusions

[ceptimus]

Keep your eyes focused on the center +, and after a while you will see only a rotating green dot, and no pink.

But really, there isn't any green in the picture at all, and the pink dots never disappear. Shows how easily your eyes and brain can be fooled.

Found on this website.

[ceptimus]

There is nothing moving in this image.

[Leesifer]

I love those.

[Dingfod]

I thought I was feeling dizzy before looking at that last one. Wrong. Now I am feeling dizzy.

[slimshady2357]

I think one of the best optical illusion I've ever seen is this one:


The two coloured squares marked A and B are the same colour! Try cutting and pasting them side by side in paint or printing it out and cutting one out and placing it next to the other to see this.

[Crumb]

Man you guys already posted the good ones. Well here is one more.



There are no black dots at the intersections.

[Ymir's blood]

Very interesting.

The second one that ceptimus posted is quite fascinating. I printed it out and the effect still works, though diminished as the colors aren't as vivid. If it didn't clash with the décor so much, it might get framed and hung on the wall.

slimshady2357's entry is the one that is most puzzling to me. I opened it in Paintshop and verified that the color in the lettered squares are (almost) identical. Copying one and moving it to the other shows that they are indistinguishable to the naked eye, though they appear so radically different in their respective places.

Shows how easily your eyes and brain can be fooled.

Regardless of whether or not an objective reality can be shown to exist, the reality with which we interact is limited entirely to what we can sense. Perception is reality, at least as far as the brain is concerned. Things like these are interesting to me because they show how difficult it can be to accept what we know to be true when out senses say otherwise.

[Crumb]

Here is one for you YB:

[Dingfod]

Well, I'll be damned. They sure as hell don't look like the same color in the original. In fact, as soon as I used the crude Paint erase around each square the illusion went away.

[Ymir's blood]

I've got a similar one saved to my hard drive, "All is Vanity", by C. Allan Gilbert, I found it at Wikipedia a few weeks ago.

Here is the page it's on:

"All is Vanity", by C. Allan Gilbert, (1873-1929)

[Ensign Steve]

Originally Posted by Warren

Well, I'll be damned. They sure as hell don't look like the same color in the original. In fact, as soon as I used the crude Paint erase around each square the illusion went away.

That makes a lot of sense, considering it's the surrounding darker or lighter squares that make the original squares appear lighter or darker.

The first one cep posted blew me away. A friend emailed it to me a couple weeks ago.

What is with the maroon lamdas on the second picture? Is that supposed to add to the effect or anything? It seemed to have an anchoring effect, as the outer-circles don't move at all. I wonder if they would move if the lamdas were gone?

[Crumb]

Originally Posted by Ensign Steve

What is with the maroon lamdas on the second picture?

I think those are snake tongues, making the picture look like moving snakes.

[Ensign Steve]

Oooohhhh...

[davidm]

In the case of the first example, the Web site from which it is taken describes the rotating dot as pink. I don’t think that’s really the case, though. I think the rotating dot is the same gray scale and color as the gray background of the picture. It always seems to disappear when it is between the stationary violet-red dots over which it is rotating, and this fact suggests it is the same color as the background.

If you placed a gray square over a violet-red background square the same color as those violet-red dots, the gray square would appear greenish. This is an example of complementary contrast. Reddish colors are on the opposite side of the color wheel from greenish colors, and they cause mutual intensification of their chroma when placed together. This phenomenon even works with gray: It will appear greenish against an intense violet red. Another way to see this is to stare for a long time right at the center of some very bright red-violet color. Then close your eyes and quickly turn away. You will see that square very vividly as an after-image, and it will be bright greenish.

Color vision is concentrated at the center of the eye. Light-dark vision is concentrated at the perimeter of the eye. Hypothesis: staring at the black cross at the center of the image gives the illusion that the red-violet dots disappear, because peripheral color vision is weak, and the greenish dot is rotating just rapidly enough that the brain does not have time to process the weak color input of the red-violet from peripheral vision. The rotating gray dot appears vividly greenish because of the complementary contrast described above. It seems to me that if you stare fixedly off to the side of the picture, the violet-red dots disappear as well, though the phenomenon is strongest when staring at the black cross.

The movement in the second example, of the violet and yellow spirals, happens for exactly the same reason. Violet and yellow are on opposite sides of the color wheel, and mutually intensify each other’s properties. The illusion of movement is intensified by the spiral structure, which itself suggests movement. However, if you stare very fixedly anywhere at this image, and wait about five seconds, the movement will stop. It will do so for the same reason as the violet-reds disappear in the first example: weak color inputs from peripheral vision. Because the color input is weak, the violet-yellow contrast diminishes, and it is this contrast that caused the illusion of movement in the first place. Sustaining the illusion of movement depends on the eyes constantly roving over the image, which is what they are naturally inclined to do. Probably the illusion of movement would also stop if this were converted to a gray-scale image, and certainly would stop if the colors were closer together on the color wheel or had less light-dark contrast.

The checkerboard example also depends on complementary contrast, this time of gray scale alone. Square B looks so light only because it is surrounded by much darker grays on all four sides by the shadow cast by the cylinder. I suspect that the shadow surrounding it on all four sides is necessary for this illusion. If the shadow were removed on even one of the sides, Square B would already begin to appear much more like Square A.

All of which shows that colors and tones are relational. There is no such thing as a color or tone except in relation to the colors and tones of its surroundings. There is no color or tone “in and of itself.”

[ceptimus]

This should fix it

[ceptimus]

oops! My previous post seems to have broken the page, and I can't edit it. Will an admin delete it please?

Edit to add: Okay. I fixed it from this PDA.

The html that is now a link was previously an iframe. The javascript in there broke this page, and I couldn't delete it from a regular browser. But I could from this PDA for some unknown reason.

[Ensign Steve]

Your post is doing something to the page, cep. Nothing below your post will render. Did you forget to close a tag again?

[Ensign Steve]

Oops. Now I realize it was pointless for me to post that (or this) as it won't render either.

[Ensign Steve]

If I wanted to post seven more of these, I might be able to force it to the next page. But I'm not gonna.

Anyway, the pull-down menus at the top of the page are broken, too.

What did you do?!

[Ymir's blood]

I PM'd ceptimus about the problem, Ensign Steve. I don't know that much HTML so can't say what's wrong with his code.

If you ignore the post, the thread seems to revert to normal.

[JoeP]

Oh. I pm'd about the problem too. I predict swift and decisive action. I can't even see the 'ignore post' button: must be because I'm a leftie.

[Ensign Steve]

I didn't even know lefties still existed! What is it like, Joe?

[Shake]

Similar to the one in post #2 of this thread:

[Shake]

And then there's this one:

[Ensign Steve]

* Ensign Steve puts on Dark Side of the Moon and lights up a stick of Nag Champa.

That last one seriously moves!