Optical illusion of the day


Interesting take on this one:

I know how it works, but my brain doesn’t. Gets me every time.


Now pull my finger


If you stare at a checker board long enough you start to see a fish…

… Keep looking…



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Don’t get it. With my finger across the middle it looks exactly the same except now my finger’s in the middle. What’s supposed to change?


I don’t see it either. Top looks darker. Cover seam, and top still looks darker. I feel like this illusion is just being presented wrong because the real surprise is that the solid bits away from the gradients are actually the same shade of gray.

I like the checkerboard setup a lot more.


Saw that on Kottke, didn’t work for me there either. What causes some of us not to see the topical delusion?

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Maybe the instructions are unclear? In any case, it worked well for me.

The image looks like it’s a 3D shape, say an open ring box with its hinge pointed towards you, with the top half dark and the bottom half light. When you cover the seam with your finger (including the shadows) you see that both halves (except for the shadows, now covered) are exactly the same shade of gray.

The point of the illusion is to show you that perception happens not in the eyes but in the brain. The brain processes the image, and it knows that the bottom half is in shadow, and so when it sees the grey in the bottom it automatically makes us see a lighter color, because it’s interpreting what the color would be in full light.

I had to tilt my laptop to get the effect that, with the seam covered, the top and bottom were the same shade of grey…so I am not sure quite what is going on.

Since they are, in fact, the exact same shade of gray, you shouldn’t need to tilt your laptop. Maybe not enough of the seam was covered? I held my finger in the air, not right on the screen.

Tilting your laptop screen will darken the light colors, so decrease the contrast, so will make shades all look like the same gray – but in this case that isn’t necessary.

Like typos that our brains ignore because we know what the correct spelling should be, this “illusion” only works because it is wrong (more or less impossible in real life) and our brains are “fixing” it for us.

Well, didn’t work for me either, perhaps because the two fields are not actually identical. The top panel has highlights near the round edges, whereas the bottom one is practically uniform. If I squint just right, I can convince myself that the core plateau color is the same, but the two objects nevertheless remain distinguishable which takes away a lot of the effect.


There is sort of a ‘meta’ component to this, no?

we all see through various ‘screens’…and some screens are clear and some are clouded…and some take manipulation to see clearly…hmmm.

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Came for the checkerboard, leaving satisfied.


Josef Albers’ Interaction of Color app is a fun black hole of time in which you can create these sort of illusions. Or get the book and some Color-aid paper.

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The instructions are unclear.

I read it as cover the seam of the objects. While it should be “cover the entire horizon line” of the picture.

Which isn’t possible with just a finger on a normal sized monitor at the resolution shown.

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For this one you don’t have to cover your screen


Didn’t work for me at all just covering the seam (shadowed places too). Waaay too many other things going on including the sky, ground, and other shadowed areas on the objects to still throw off the eye.

To work for me, I had to block the top and bottom and sides of each square. Making two "V"s with my fingers, perpendicular to each other, did it. The two flat sections that peek out do indeed look the same color then.


There would also be a similar white highlight on the grey top if both parts were the same color in the light scenario described in this image. There are also imaginary white/ black environment reflections on the sides of this thing that have nothing to do with the environment/ lighting in the image.

This isn’t really even an illusion. It’s an observation of the type of light/ color relationships artists painters and illustrators deal with on a daily basis. All this image illustrates is that the color white turns grey when in shadow. Is that supposed to freak me out?