26 December 2007

Checkershadow optical illusion

One of the best optical illusions I've ever encountered:

The squares labelled A and B are exactly the same color.

Here is a proof in which the first illustration has been overlain by two gray bars; note how the bars blend equally with square A and square B.

No matter how many times I look at this, and no matter how logically I think about it, I still cannot wrap my mind around the reality.


  1. according to the pattern its not suppose to be the same color. The gray bars is the illusion...

  2. my brain just exploded

  3. Amazing what we can see that our brain does not interpret properly.

    Benjamin Koshkin

  4. Well, I wasn't buying it, but I meticulously covered up everything but the the two squares and voila (!) they were indeed the same color...

  5. Damn! Could not belive it, so i checked i photoshop, and it's the same mo'fo' color!!

  6. Just look at A on the first picture, then B will "transform"

  7. i opened it in photoshop and the colors are not exactly the same the color codes i get are #787878
    and #767676.. since thats not an exact match this illusion is bullshit

  8. the colors are both 787878.
    this is legit

  9. could not believe and still not... but same color in photoshop. however it's amazing...!

  10. From the the picture I observed that the cylinder has cast a shadow on B, try removing the cylinder and see if the illusion still persists. Come to think of it, what is the significance of the cylinder in the first place?

  11. The bars are the color of square A and the Square B is a different color.

    I think this is happening:

    Different people have different computers with different color settings. I think it looks different depending on what computer you are using.

    I covered everything up but square A, then everything but square B and they were different colors.

  12. @Bodson:

    The purpose of the cylinder is to give a reason for the shadow to exist. The illusion still works without it, but then there would be no 'logical' reason for the shadow to exist. Since the shadow is the cause of the illusion (the human brain does not see colors individually but by comparing it to its surroundings), it helps to increase the realism of the illusion.

  13. square A and aquare B are the same color, i'll be darned. I checked them in photoshop each is RGB 120/120/120

    copied the A square and when I move it around the screen it looks like it changes color.

  14. For all of you are claiming it is BS and using photoshop to check, you don't need to. There is an easier way.

    I took a paper towel covered my monitor.

    I then tore a hole over only picture B.

    I could see that the bars blended perfectly. I could not even see where they began.

    I then did the same thing to A, with the same result.

    I then did the same thing, with only the bar showing. I used two pieces of paper for this. I could see that the bar was a solid color.

    That is a way to visual be astonished by the illusion.

  15. Due to jpg/gif conversions, the exact RGB colors may have changed a little, but olnly in a negligible measure. I'm sure the author's original file had exactly the same colors in both squares.

    Try in Photoshop: color one of the squares exactly with the other square's shade.
    The illusion still works.


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