Wednesday, April 11, 2018

Do your eyes play tricks on you?

Do you see things exactly as they are, or do your eyes play tricks on you? Check this diagram:



Are the horizontal blue bands tilting up or down? Are they straight or do they twist and bend? Or are they straight and level?

If you hold something straight up to the diagram, you can verify that the blue bands are actually straight and level.

This optical illusion by Victoria Skye is a variation on the famous "Café Wall Illusion," in which rows of black and white tiles are slightly offset to the right and left to create a strange tilting effect.


Optical illusions remind us that our eyes — really our brains — do indeed deceive us. That's why we need to use the methods of checking lengths and slopes if we want to achieve accuracy in our drawing. 
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Read more
Previous post (2009) on the Cafe Wall illusion
An interactive version of the Café Wall illusion with sliders that lets you change parameters
Pop Culture Cafe about the Skye illusion
Explanation of the illusion by Richard Gregory

6 comments:

rock995 said...

Yes, amazing how our brains interpret those signals from our eyes. I knew this illusion from one I've seen before but this was even more convincing visually. "No question those blue lines are slanting" I thought but was just remembered enough to allow my eyes to dart quickly from the spot on the left border where the band began to it's corresponding exit on the right border and then it was easy to see those points were the same height on either side. Whew!

Mel said...

Indeed, the alternating direction of the cell fiber connectors between them does the trick. If I step back 3 yards from the computer screen, the illusion is no longer there. Just rows of alternating light blue and black blocks. The devil is in the detail.

Annie C Curtis said...

Narrowing your eyes also dispels the illusion, but unlike the vase/2 faces or old woman/youn girl, the illusion comes back in full force when you open your eyes again.

Carole Pivarnik said...

That is a great optical illusion! It is kind of unpleasant to look at for long, perhaps because something about it just seems wrong. I'm surprised when drawing at how often what I think I see and then make a mark for is wrong compared to the actual subject. I end up making lots of corrections unless I really pay attention to relationships of shapes and use small reference marks to keep track of those.

Peggy Aare said...

I believe the above illusion is not comparable to the cafe wall illusion with its shifted contrasting squares. Instead I think the illusion is primarily due to the orientation of the small black and white 4-squares at the corners of the black squares, reinforced by the assymetrical decorations on the blue bands. Look up Bulging Checkerboard Illusion.

James Gurney said...

Carole, yes, I also found looking at it to be uncomfortable and compelling, making me want to keep checking it to see if I was crazy.

Annie and Mel, yes, the distance does affect the impact, which must mean that those little black and white squares and the offset pointy shapes have to be visible.

Peggy, I mentioned the cafe wall illusion in reference to this one because the inventor invoked it, and also because the effect of the illusion is similar (illusory diagonals in the peripheral vision). You're right, though, that the visual mechanism is different.