Believe nothing of what you see...

[netmaestro]

Here is a little picture you can amaze your friends with (and maybe make a bit of money on bar bets)



You can use Photoshop (or similar) to verify that the sqares marked A and B are indeed both rgb(107,107,107) but to look at the picture it is nearly impossible to believe. It's all done with shadows...

[DoubleDutch]

nice

[rsts]

- but to look at the picture it is nearly impossible to believe.

You're right, It's hard to believe, but colorpic confirms it.

Pretty nifty.

[netmaestro]

I know I said it's all done with shadows, but that isn't strictly true. Part of the effect is caused by the shadow thrown by the cylinder, but it's what your brain does with the shadow that makes it work. The checkerboard pattern is well established in your mind when you look at the picture and your brain "wants" the B square to fit into the pattern - so when the shadow falls on it the brain tries to compensate for that and interprets the square as being lighter than it really is.

[ricardo]

The squares or the letters inside (A,B)?

[Dare2]

lol. That is amazing.

[ricardo]

OMG!

Hard to believe it!

I will make some bucks with a couple of friends

[jack]

stupid mind
i made a printout and then cut out the squares, they are the same color.

[netmaestro]

Best way to win bets with this is to print the picture out and make a template out of a second sheet of paper. Put the second sheet over top of the picture and trace around the edges of the two relevant squares. When you have this done, cut them out with a pair of scissors. Then, to prove the colors are equal, you can just place the template over the picture, hiding everything except the two squares A and B. They then appear identical. Don't bring your laptop to the bar, it'll get stolen.

[MrMat]

You can test it interactively on this site:
http://www.echalk.co.uk/amusements/Opti ... ption.html
There's a couple of other colour illusions there too, check out illusion 3!

[netmaestro]

Those indeed look remarkable when viewed interactively, but photoshop's eyedropper does not prove them out like it does in Adelson's picture. I'm getting significantly different readings between the relevant squares in all the examples. I think somebody took a good illusion and tried to stretch it a bit further by using colors that the naked eye would see as identical with the mask applied, but you can't fool photoshop. Even my naked eye sees the difference in example 1 with the mask on.

Also - The interactive examples are done in Flash, and with a Flash presentation virtually anything could be going on subliminally, which is not the case in the first picture.

[PB]

> Even my naked eye sees the difference in example 1 with the mask on

Edit: Actually, I agreed with you at first... but then I took a screenshot of
example 1 with the mask on, zoomed in, and looked at it with Paint Shop
Pro... both squares were RGB 107,107,107... so I don't know why PhotoShop
is giving you different readings?

[thefool]

I tested it too, just using paint brush no need to launch photoshop here.
I take the colour, and draw using the colour it find on the second square.

The pictures in the link, in the flash, are real. But i agree its easy to cheat, but in this case it isnt cheating.

[netmaestro]

I took a screenshot of
example 1 with the mask on

GOTCHA! Try it with the mask off. Proof positive that skullduggery is afoot!

[PB]

> GOTCHA! Try it with the mask off. Proof positive that skullduggery is afoot!

Nope, still get 107,107,107 for both squares.