Thread: Visual Phenomena & Optical Illusions

I thought it might be nice to open a thread and start a collection of people´s favourite optical illusions and maybe related stuff.


Here is something I find very impressive:



The thing is - you back away from the screen - I had to go to the other side of the room, but I have good eyesight...
And the faces swap expressions - the left one looks calm and the right one looks angry ..
Go closer and it reverts back.

Originally Posted by grandillusions.com

When we look at an object, we can normally see both fine detail and coarse detail. However when we are close, the fine detail will dominate, and when we are further away, we lose the fine detail, and see more of the coarse detail.
Both of the faces you see above are hybrids - each face is actually a combination of two faces. The left hand face shows an angry man in fine detail, but within the picture there is also coarse detail of the calm face. Move away, and you lose the fine (angry) detail, and just see the coarse (calm) detail.
The right hand face shows the calm face in fine detail, and the angry face in coarse detail.

What made me think of this thread in the first place was an age-old thread about one of my favourites of all time.
The Spinning Girl Illusion:

The following is a mix of my own words and an edited quote from on here: neurologicablog.

Take a look at the spinning girl above. Do you see her spinning clockwise or counter-clockwise? I first saw it spinning clockwise, and I had a hard time getting it to switch direction. Today it started counter-clockwise and tends back there.
Give it a try!

The visual system evolved to make certain assumptions that are almost always right (like, if something is smaller is it likely farther away). But these assumptions can be exploited to create a false visual construction, or an optical illusion.

The image is not objectively “spinning” in one direction or the other. It is a two-dimensional image that is simply shifting back and forth.

But our brains did not evolve to interpret two-dimensional representations of the world but the actual three-dimensional world. So our visual processing assumes we are looking at a 3-D image and it uses clues to interpret it as such. Or, without adequate clues it may just arbitrarily decide a best fit – spinning clockwise or counterclockwise. And once this fit is chosen, the illusion is complete – we see a 3-D spinning image.

Tips:
Look around the image, focus on the shadow or some other part in the picture -or what works best for me - read the text of the post while having the illusion in the peripheral field of vision too and switch attention.

So you may force your visual system to reconstruct the image and it may choose the opposite direction, and suddenly the image will spin in the opposite direction.

Since I can´t put text next to it - you could zoom out your screen-view to see her (partly).

It is unfortunate that this illusion is sometimes put forth to support the myth about people being either more right-brained or left-brained.
See the link above for arguments.



By the way - I was a bit shy to open new threads and when stumbling over this pet illusion of mine and vigorously posting - I came to learn a new word!!
I do realize now what "necroposting" means and that it is indeed not a good idea..
Made me smile, this expression.

Looking forward to seeing, what you find cool - I like going search-surfing for such things and will surely follow up!
Oh - and - out of context - but I love this smiley and might put it as an end point again..