Optical Illusions | Vol. 3 / No. 30.1

Are there really only three colours in this picture? | Image: Akiyoshi Kitaoka

So yesterday I stumbled across this post over at Mental Floss. It’s basically saying that, in the illusion image above, a piece by artist Akiyoshi Kitaoka, there are only three colours, and the “green” and the “blue” are both the same colour. Look again below:

Image: Akiyoshi Kitaoka
Image: Akiyoshi Kitaoka

It’s pretty freaky. They really do look like different colours, but in large part they’re both turquoise, and the difference is due to the way our brains perceive neighbouring colours. Note that the stripes going through the “green” are orange, while those going through the “blue” are purpley-pink.

But I was in such disbelief that I downloaded the image, zoomed in, and checked with my colour dropper in GIMP. And here’s the thing: I think the image processing being done by whatever’s doing the jpeg compression is having a problem similar to our eyes.


When you zoom in, you can see that the wider-striped areas do indeed have very similar colours in them. Not perfectly the same, but close. But the thinner the stripes get, the more compression has an effect (needs moar jpeg, etc., etc.). The greener stripes really do become greener and the bluer ones bluer.

So, yes, it’s a very cool optical illusion, but if you’re concerned, try not to be. Apparently, it’s even fooling your computer.


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Richard Ford Burley is a human, writer, and doctoral candidate at Boston College, as well as an editor at Ledger, the first academic journal devoted to Bitcoin and other cryptocurrencies. In his spare time he writes about science, skepticism, feminism, and futurism here at This Week In Tomorrow.