Replies to Msg. #739501
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 Msg. #  Subject Posted by    Board    Date   
19134 Re: Illusions...
   Actually, I found I could see the circle when focusing on tracing the...
lkorrow   CONSTITUTION   05 Aug 2012
8:33 AM
19132 Lesson of the Day Award - Popple Illusions. Thank you, Due - Re: Illusions...
   Wow - that second one was even tougher on the eyes than the first. I...
monkeytrots   CONSTITUTION   05 Aug 2012
7:41 AM

The above list shows replies to the following message:

Re: Illusions...

By: DueDillinger in CONSTITUTION
Sun, 05 Aug 12 6:46 AM
Msg. 19130 of 21975
(This msg. is a reply to 19128 by lkorrow)
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Close one eye and hold something round out in front of the image until it matches the size of one of the shapes and you'll see that they are indeed quite circular.

This is called a phase-shift or Popple illusion.
Here's a variation:

Uploaded Image

If you want a real explanation, it'll cost ya...

http://www.sciencedirect.com/science/article/pii/S0042698904003694

The eye is easily fooled. The rings below are concentric.

Uploaded Image

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