It's an Hoptical Illusion.

The 'blue' and the 'green' are the same colour.

I'll leave it as an exercise for the reader to explain how it works .

What Blue?

how does it "work"?

How does what work? Is it moving? I can't detect anything special.

regards,

Vulcan

Then try the "What's surprising" bit of the question.

I'm not sold that they are the same color. Sure look night and day difference to me.

You are implying that when I print the picture in color, the printer is going to use the exact same toner mix to create the "green" as it does the "blue"?

I see no geometric reasoning which would make me believe that my eyesight (which is not colorblind in any way) could possibly be fooled to the point that the two quite distinct colors I am comparing, are in fact the same.

Please make me believe it... Cause right now I'm having a hard time... No in fact, I just plain don't buy it.

Upon a closer look with photoshop, I have decided that the internal color of each is the same... the "Blue" looking bit is outlined with blue, while the "green" looking bit is not. In addition the contrasting color is different, causing the perception to be fooled... that works quite well... I wasn't sold at first... so I had to take a much closer look, now I'm convinced.. well, actually I have the proof that I needed... The internal color (disregarding the different outline) is R3,G253,B150 on both of the colors in question. Interesting.. very interesting.

0, 255, 150 plus the fringing isn't there in the original (see below), but I guess GlobalSpec made a few changes to shrink the image. Still the illusion is still pretty surprising (to you and me anyway).

For completeness:-

What is it? An optical illusion.

What's really surprising? The bluish colour and the green colour are identical.

How does it work? Your eye compares the green looking colour to the orange in one spiral, and compares it to the pink in the other (I think).

It came from here.

And, I was pointed there from Clive Maxfield's blog on pldesignline.

This is the magnification of the "blue" stripe. IT HAS BLUE IN IT! The explanation could be in the capability to resolve green and blue. This should be doctor's forum puzzle!

I got the same effect when pulling it into Paintshop Pro & zooming, but I think this is down to the attempt by the software to stretch a gif image. If you leave it small & go in carefully with the dropper tool, I think you'll get R3,G253,B150 (as RVZ717 found).

It was drawn to my attention a few days ago by a mate on facebook (which is how come I jumped in with #1 in this thread ), who cited the Discover magazine article (pointed to by Randall), which in turn cites http://www.psy.ritsumei.ac.jp/~akitaoka/color12e.html, which shows how it works (but is still hard to believe at first sight).

Wow loads of stuff from Akiyoshi's illusion pages http://www.ritsumei.ac.jp/~akitaoka/index-e.html

I liked these scintillating sapphires: not sure how well they will come out on CR4.

How what works? Should there be something moving? The yellow does twitch a bit though, Ky.

My wife says its a Nautalus Mandala. "What's that?" -"Some Zen Bhuddhist thing."

Hi Randall ...

Here's a closer look at the BLUE and GREEN lines ... hmmm ... they ARE both GREEN .

Kind regards ...

In my opinion, it's not an illusion at all. The GIMP shows it to be a mess of colours that most image display applications can't cope with.

Okay, I have a sudden (hopefully BRIEF) interest in optical illusions ... check this out http://www.puzzle.dse.nl/tests/index_us.html#color_reading (sorry if the link isn't clear ... my browser isn't cooperating). SO, you hear that "if you don't stop, you'll go blind"? Well, these aren't nearly as fun, but they ARE interesting ... and the one with the spiral is absolutely FREAKY. Enjoy. Kind regards ....

Does it come in a box of pain killers?

Not sure of the origin of this one ...

... but it moves for me.

Is it a chopper disk for some sort of focus/aiming device. The broad lines give a coarse output then the narrow lines give a sharper pull onto focus.