Does Big Ben look like it’s leaning over more in the right hand image than in the left hand one? It can take a double-take to spot that the two pictures are identical. I find it a fantastically strong illusion.
It’s a demo of a new illusion found by Frederick Kingdom and colleagues (you’ll need to scroll down that link to get to their bit – look out for an even more than usual Leaning Tower of Pisa). Their discovery is a new version of the size-constancy illusion. This is my second demonstration of it – a few posts back I used a picture of a historic streetlamp. But here’s an example that looks stronger to me, with a better known subject.
Update 10 Oct 2011. Big Ben really is leaning over! But not (yet) as much as it appears to lean in this illusion.
No just took at different angles
No, they’re not taken from different angles! If you know how to view picture pairs as stereo pairs without a viewer, try making this pair of pictures overlap, and you’ll see they’re Identical. (For how to do that, I think any of our stereo picture posts will give you links). Or download them and try overlapping them in your picture editor. I agree it’s such a strong illusion, it’s hard to believe.
Ironically enough, Big Ben is leaning, 8.6″ to the northwest.