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Wednesday

Color Contrast Optical Illusion

The below two cubes share some things in common. The creator of this optical illusion states the following.

"Despite the fundamental difference in the apparent colour of the 'blue' tiles on top of the left cube, and the 'yellow' tiles on the top of the right cube, all the tiles are in fact physically identical (grey in both cases)."
I'll take this one step further and let you know that the RGB value for all 11 squares mentioned is exactly the same R:136 G:136 B:136. The blue and yellow squares mentioned are the exact same color as the gray block to the right.

Dale Purves M.D.
R. Beau Lotto
(c)2007

But they are not the only tiles on these cubes that look different but are exactly the same. Can you spot the other tiles that look different but are actually the same exact color?



The truth is that the optical illusion for tiles numbered 1 are the result of color contrast and the optical illusion for tiles numbered 2 and 3 are the result of brightness contrast.

With that said you must have no doubts that what I'm stating as fact is true. What's that you say? You don't believe it? Ok, OK already, quiet down. I guess we will just have to take the steps needed to prove that I am correct.

Project: Proving all the 1, 2, or 3 tiles are respectively all the same color.

There are a few ways you can prove that the tiles are the same color.

Before we continue, right click on the top image and open it in a new window. Now you have an image to work with.

1) You can use a graphics program like Photoshop, Paint.Net, Gimp or the Colorzilla extension for Firefox browser.

My choice is Colorzilla w/Firefox. Using the eyedropper tool you can determine that the RGB values of the respective tiles are the same, for number 1 tiles the RGB value is R:136 G:136 B:136, number 2 tiles have a RGB value of R:182 G:159 B:14, and number 3 tiles have a RGB value of R:75 G:45 B:138.

Not good enough for you, heh? Still not ready to trust that the computer is correct or you don't have an eyedropper tool? Either way you can move on to step 2 or 3 below.

2) Cut out a cardboard mask.

By viewing patches of the squares without the surrounding context, you can remove the effect of the illusion. A piece of cardboard with holes created in the right spots will work as a mask for a computer screen or as a mask for a the printed illusion. Holding up this mask to the image on the screen or printed paper should be enough to convince you. But if you were like my daughter nothing but this next step would do.

3) Print the image and cut out the respective tiles.

WARNING: Do Not use any specialty scissors your mother or wife uses for any kind of crafts, IE. quilting or fabric scissors. Doing this can be hazardous to your short term happiness. When in doubt get permission to use the scissors first.

This is another way to isolate the patches from their surrounding context. Cut out each tile along the edges. Remove them. Hold them side by side. Overlap the cut out tiles. Yup they're the same color. No denying it now, is there?

Please note that I have heard that some printers have "enhancement" processing that increases the contrast of edges. This can cause the printed squares to have slightly different RGB values. I haven't run into one of these printers yet where the overlapped squares didn't look identical, but your mileage may vary.

4) Of course you could just go to the interactive demo that the creator has up on his site. He shows both the color contrast and brightness contrast illusions, plus a few more that will make you think twice about believing what you see.





13 comments:

Scary said...

These type of illusions always confuse me. Good one though.

Anonymous said...

OK, I tried the cardboard mask, even before you suggested it - and they are not identical. In fact, they are exactly as the eye sees them, quite different and distinct in color. No illusion at all.

Walt said...

The colors on the screen are 100% identical as indicated. If your mask didn't convince you maybe you were looking at the wrong squares. Go to the site listed in number 4 and use the online mask.

One of the best illusions around especially since you still can't see it.

Color id using Colorzilla or Photoshop doesn't lie.

Cut them out and overlap them.

Good luck.

Anonymous said...

Actually, your first means of showing it is an illusion is not valid. This test just shows that the computer is trying to draw the same colors, not that it succeeded. The effect could thus be arising because of an optical illusion, or do to defects in monitor technology. It could be the effect is caused by the fact that all monitors when asked to draw a grey box in a yellow background are only capable of drawing blue boxes. Your daughter was wise to reject this test.

The other tests are valid tests. However, if you use lightweight office paper to create the mask, this test can fail as enough color can leak through.

tom said...

OK, I tried it with a cardboard mask, and the colors were completely different. So to follow up, I just downloaded the image and looked at it under Photoshop, with the color dropper tool - again the colors are completely different. On my computer, at any rate, there is no illusion.

Walt said...

The only thing I can conclude is that you are comparing the wrong squares.

The Photoshop eye dropper tool confirms that the blue squares on top of the left cube and the yellow squares on top of the right cube are in fact r136 g136 b136.

Check out this page for a Demo.

Anonymous said...

"On my computer, at any rate, there is no illusion."

This is not a subjective illusion that might be different on other computers. It is digitally impossible for any other computer not to come up with the same results. Unless you process the image by resizing or changing format.

Of course if you downloaded the image from some other page it could be different due to being manipulated. But if you download the image in this post it will be the same.

Anonymous said...

There's another way to verify these illusions. Bring the image into your graphics program of choice. Then copy one area and drag it to the other for comparison. The color of the dragged area can't change while it's being dragged.

The same thing can be done if you print it out, but obviously using actual scissors. :)

Anonymous said...

Si no funciona la ilusión óptica, piensen en visitar un oftalmólogo, quizás el problema sea que sus ojos tengan deficiencias retinales, o peor aún, que las zonas de la visión de sus cerebros alojen algún tipo de cáncer o malformación celular.

Anonymous said...

i tried it to they are complete different colours!And you said the blue and yellow squares are identical in colour in fact they are not!!!!!

clowns1 said...

Those illusions are crazy!

Anonymous said...

i absolutely enjoy all your writing way, very charming.
don't quit and also keep writing in all honesty , because it just simply good worth to read it.
excited to looked over more and more of your own content pieces, kind regards :)

Admin said...

wow, i like your blog. I really enjoy it. The explanation that you give to me about the color optical illusions is so complete. Thanks' again


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