Astronomy Picture of the Day -- The Same Color Illusion

NASA ^ | October 07, 2012 | (see photo credit)

[SunkenCiv]

Explanation: Are square A and B the same color? They are! To verify this, either run your cursor over the image or click here to see them connected. The above illusion, called the same color illusion, illustrates that purely human observations in science may be ambiguous or inaccurate. Even such a seemingly direct perception as relative color. Similar illusions exist on the sky, such as the size of the Moon near the horizon, or the apparent shapes of astronomical objects. The advent of automated, reproducible, measuring devices such as CCDs have made science in general and astronomy in particular less prone to, but not free of, human-biased illusions.

[SunkenCiv]

[Credit: Edward H. Adelson, Wikipedia]

[SunkenCiv]

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[bimboeruption]

Maybe it’s my monitor, but B is lighter even when the squares are connected.

[mdmathis6]

my monitor too....even when i go to the web site...there is a subtleshade difference.

[KarlInOhio]

Or maybe it's your eyes. I saw the same thing as you but ran a program called WhatColor (http://www.hikarun.com/e/) and all the pixels in question have a RGB of 120,120,120. It's a nice solid gray.

[MestaMachine]

Photoshop says they are the same.
R 120
G 120
B 120

[MestaMachine]

Dang. Beat me by 6 seconds,

[The Cajun]

My first thought looking at the connected picture was bull!!!!
Then I put my finger and covered the *Connection*.
Amazing!!
Really freaky when you run your finger across the top square to the bottom square and then in the opposite direction.

[UCANSEE2]

That’s because you are both color-blind.

; )

[dr_lew]

All you need is MS Paint. Here I copied a section which still maintains the illusion, then blotted out most of it leaving patches of A and B, which now appear identically.

[MestaMachine]

Sometimes it surprises me how so many people don’t realize what a neat program Paint is. I use it fairly often.

For this though, I was just wanting the RGB values.

[count-your-change]

I think what we're actually talking about here is contrast and not colour as both blocks are bordered by sharply contrasting blocks. The surrounding blocks of A and B provide the same level of contrast but at opposite ends of the scale.

[Las Vegas Dave]

The Same Color Illusion Image Credit: Edward H. Adelson, Wikipedia

[martin_fierro]

There's an island cleverly hidden here.

[BlueDragon]

That chessboard is TOO SMALL! drives me crazy eyetellya...

[FroggyTheGremlim]

I believe Paint was developed by a company called Z-Soft.

Microsoft bought the company and claimed credit by calling it MS-Paint.

[blueunicorn6]

What’s with the yellow can on the board?

[MestaMachine]

I just call it Paint. It’s a very versatile program and I use it quite often.

[AustinBill]

See http://www.youtube.com/watch?v=rQJEzz-XdlA for a better illustration of this illusion. I agree this particular image is unconvincing on most monitors.

[Bellflower]

When I cover everything up around the squares and only leave a triangle of each showing, without the letters, they do not look like the same shade.