[OT] The coolest optical illusion I have seen in my life...

[Zappo]

Gaah!

To see it without photoshop, you can just cover with your hands the cylinder and as much shadow as possible, trying to leave just a bit of A and B visible. Concentrate for a moment, and you realize that they really are the same colour. Color. Whatever.

 

[Jarval]

But the brain is better at interpreting data into expected results. A couple of adages hold true: "You only see what you want to see", and "Never split up the party."

The latter makes my post OT.

But no less true...

 

[Oni]

If you do have photoshop or some other graphics program take a square of the colour and copy it so that you can move it around, if you move it between the two squares you can see it apparently changing in value (it doesn't but it sure looks like it).

 

[Agamon]

I tried staring straight at B, and sure enough it started darkening until it was the same color as A.

I love this kinda stuff, very nifty.

 

[Saeviomagy]

It just shows how good the human brain is at doing it's job.

It doesn't care if the square in the shadow is the same colour as the square out of the shadow right now. It cares that the square in the shadow would be the same as the white squares if it was not in the shadow.

Just like it wouldn't care if the leopard hiding in the shadow isn't the same colour as the leopard walking along in the sun. The brain knows they're still the same thing. And that realisation could save you. While knowing the leopard in the shade is the same colour as some stupid flower won't help you one bit.

 

[Caedrel]

*sigh*

How do you think this compares for "coolness" with the my personal favourite types of optical illusions:

(1) the stereograms where you can see a 3d image in a 2d image simply by adjusting the focal length of your vision - remember all the people standing around in shopping centres staring at bits of paper and occasionally going "Wow!"

(2) the Truman Show advert where you can see a big picture made up of tiny discrete pictures. I especially liked the Star wars themed ones on this...

 

[Crothian]

Cool picture, any more of these?

 

[tarchon]

How the heck does this work? I always thought colour perception was something the human eye was good at.

It's because what your brain maps is the contrast, not the absolute intensity (or even the absolute spectral intensities, the true color - you really perceive a sort of relative color). The range of optical intensities encountered in the real world is so immense that even images with logarithmic absolute response would require processing unwieldy amounts of information. Thus the brain doesn't bother paying much attention to absolute intensity values and works with contrast levels instead. The really sophisticated bit is that our optical perception is capable of seamlessly integrating varying intensity reference levels within in the same scene to produce an apparently continuous and uniterrupted map of the contrast. This is one reason why you can perceive a scene with mixed light and shadow quite easily, while if you take a photograph of the same scene, you either have to settle for having the bright parts of the scene washed out or the shadowed parts completely black.

 

[Celebrim]

Who, seeing is believing.

Or, rather seeing is not believing.

Or whatever.

Anyone whose taken a photo editor to this thing knows what I mean.

 

[BMF]

Notice also that the "A" is in white type and the "B" is in black type, thus heightening the contrast of the squares they are in. Very subtle and very cool.