The Optical Illusions Appreciation Thread

Yithian

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...and posted earlier.

And commented upon by you.

(You said it was great but suggested I edit out my description of what was shown. I did and you edited out your advice to save the magic.)
 
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Krepostnoi

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I've just seen a tweet which suggests everyone else in the world but me knows this already. I am feeling anxious and need reassurance (joking, but not really). Please tell me truthfully: assuming a standard deck of playing cards, how many actual number 8s do you see on the 8 of Diamonds?

cod-8d.jpg
 
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Peripart

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It took me a while, but I see what you mean - there's a sort of shadow 8 in between the diamonds. I'd never had it pointed out before, so you're certainly not alone! That said, I don't think it's been designed that way, it's just coincidental.
 

Schrodinger's Zebra

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Focus on central figure. Observe and note direction of spin. Focus on left or right figure. Observe direction of spin. Return to centre: direction of spin has changed. This is clearly mind control. Explanations? Clearly you use the guidelines on the outside figures for reference, but why is it so hard to 'overrule' one direction of spin without them?

View attachment 10009

I have just noticed is that the RH figure (who makes it go anti clockwise) is standing on her RIGHT leg whereas the LH figure (who makes it go clockwise) is standing on her LEFT leg.

I have absolutely no idea why that matters but I guess it does somehow...?
 

pandacracker

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look at the negative space, the gaps between the bollards/balustrades. Follow the outline of one of the gaps.

Does that help?
 

hunck

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The Pinna-Brelstaff illusion

As you move closer the orange bits move clockwise, further away counter clockwise.



And here's the explanation if you can make sense of it.

Andolina and his colleagues trained two macaques to indicate whether they saw any rotation in images that were actually in motion. Then they showed them the Pinna-Brelstaff illusion, and found that the macaques perceive illusory motion similarly to nine human observers.

The team found a 15-millisecond delay between the activity of neurons that perceive global motion – in this case the illusion that the entire set of lines is moving – and those that perceive local motion, in this case that there is actually no movement.

Our brains probably have the same delay, which may seem like a flaw, says Andolina, but they are just being efficient. When we see something, our brain tries to quickly guess what it is. Normally, that guess is pretty accurate because the physical rules of our environment are usually consistent. Here, your brain is using a shortcut, substituting apparent motion for actual motion.

“As you move your head in and out, the way these elements slide across your retina is going to have two motion directions: an outward expansion, but also the rotation induced by the fact that the edge is slanted,” says Paul Azzopardi at the University of Oxford. “That’s different from something that just rotates or just expands, so you might expect that it takes a little more work to resolve what the motion is telling you.”
 

escargot

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Feast your eyes on Techy at Hest Bank in Lancashire.

It might be just me, but the sign looks weird. The posts don't line up with the board on top. It's as if the whole thing changes direction halfway up. When I made Techy stand there for the photo everything looked normal.

(The point was partly to show how dangerous the beach area is. Right behind me there is the very busy railway level crossing. We were lucky to get out alive!)

I also snapped another view with a bench which seems to change the direction it's facing. In fact I said 'Let's sit on the bench over there! Oh no, it's facing away from the sea, how pointless. Er, 'old on, no it's not, whats going on?'


Hest Bank.jpg
 

Krepostnoi

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Feast your eyes on Techy at Hest Bank in Lancashire.

It might be just me, but the sign looks weird. The posts don't line up with the board on top. It's as if the whole thing changes direction halfway up. When I made Techy stand there for the photo everything looked normal.

(The point was partly to show how dangerous the beach area is. Right behind me there is the very busy railway level crossing. We were lucky to get out alive!)

I also snapped another view with a bench which seems to change the direction it's facing. In fact I said 'Let's sit on the bench over there! Oh no, it's facing away from the sea, how pointless. Er, 'old on, no it's not, whats going on?'


View attachment 20166
Is it because the foot of the left-hand post (as we look at it) is obscured behind a tuft of grass? I'd hazard that our brains want to interpret it as being the same height as the right-hand post, and so we assume it is in fact further away from the camera than its companion. Great illusion, though. Now then, what's this I hear about a bench?
 

escargot

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Is it because the foot of the left-hand post (as we look at it) is obscured behind a tuft of grass? I'd hazard that our brains want to interpret it as being the same height as the right-hand post, and so we assume it is in fact further away from the camera than its companion. Great illusion, though. Now then, what's this I hear about a bench?
Yes, I think that is it - posts are the same size, just the left one is partially obscure.

Now, about that bench, eh?...
Next time we're there (not too long away I hope, it's lovely spot) I'll take another photo from as close an angle as possible without the bike and see how it looks.

The bench photo might be disappointing as it's a long way off but I'll round it up anyway!
 

blessmycottonsocks

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Feast your eyes on Techy at Hest Bank in Lancashire.

It might be just me, but the sign looks weird. The posts don't line up with the board on top. It's as if the whole thing changes direction halfway up. When I made Techy stand there for the photo everything looked normal.

(The point was partly to show how dangerous the beach area is. Right behind me there is the very busy railway level crossing. We were lucky to get out alive!)

I also snapped another view with a bench which seems to change the direction it's facing. In fact I said 'Let's sit on the bench over there! Oh no, it's facing away from the sea, how pointless. Er, 'old on, no it's not, whats going on?'


View attachment 20166

Nice one!
It's vaguely reminiscent of one of those Escher Tri-Bar statues:

PSX_20190920_112203.jpg
 
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