24 August 2018

Concentric circles




Top image hat tip to Alex Santoso, who found this excellent optical illusion on Twitter and posted it at Neatorama in 2012.  Reposted to add the bottom one, via.  The two illusions are based on the same principles; I believe the lower one was just modified to bring the inner circle closer to the outer one.

11 comments:

  1. My brain refuses to see them as perfect circles. I am aggravated at it.

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  2. Well, I just happened to have a soft drink top sitting there that was the same diameter as the inside circle and when I held it up to the inner circle it exposed the fact that it is an oval, not a circle.
    Just to make it official, I took a ruler and found the outside diameter going east-west was 5 and7/8 " while the north-south came in at 4 and 7/8".
    The larger circle is oval as well, just not quite as drastic.

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    Replies
    1. Does the same thing happen on your monitor when you view the images at the link??

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    2. Yes, that is where I tested it, but while I was at lunch I determined that it was possible the settings on my computer monitor are skewed, like Panvision, so I printed it off.
      Perfect circles!

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    3. I copied the image into Photoshop and used the measuring tool. 244 pixels width and height for the interior of the inner circle and 351 pixels width and height for the interior of the outer circle. They're definitely circles. Wish my eyes would interpret them that way without needing to rely on tools to confirm it. Sure is weird.

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  3. Optical illusions like this really tend to make me feel like my brain isn't working the way it should be.

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  4. They're actually very different circles - see how the inside circle on the upper image "changes direction" a bit before 3:00 and 9:00 (the outer does the same thing at about 12:30 and 6:30)

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  5. I agree with Paul - the rings are circular, but the white and black lines that appear to barber-pole around each ring go in a consistent direction on each ring in the bottom image (one direction on the inner ring, opposite direction on the outer ring), but change direction as Paul indicates within each ring in the top image.

    -Jean K.

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  6. Nope, I see the "changed direction" of the design, too. The pattern on the second set is twisted evenly, like rope, where the first set is twisted left then right, then left...ya think it's just our eyes?

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  7. I misunderstood the "changed direction" comment. You guys are correct that they are "different" in that respect.

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