Optical Illusion: False Curvature

Even though the middle of this square appears to bulge out, this picture is exclusively composed of squares. Don’t believe me? Just put a ruler on top of your screen and verify the fact for yourself.

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18 Responses to Optical Illusion: False Curvature

  1. OK, something's not right, then. On my monitor, the middle horizontal lines aren't perfectly straight, and do bend slightly in the middle, even against a ruler.

  2. OK, something’s not right, then. On my monitor, the middle horizontal lines aren’t perfectly straight, and do bend slightly in the middle, even against a ruler.

  3. Very cool.

    I assume you above used an actual ruler held up against the screen?

    Use "Free Ruler" on the Mac, or one I wrote for the PC a long time ago, and compare pixels to pixels. The lines are in fact all straight. The ruler image appears to acquire a bulge or a waist, depending on where you place it. But you can get it to where the line is one pixel away from the ruler edge, and use a magnifier (zoomin on the PC, or I grabbed it into an image file and used Preview on the Mac to enlarge it) to examine the edge for proof.

    You may have either a bent ruler, a bent screen, imperfections in the pixel array on the screen, or your eyes are still affected and the gap between the ruler and the screen allows more of the illusion through than you think.

    This particular image is playing off something the optical nervous system does anyway – there is one particular after-image / fill-the-dark that sometimes can be experienced which takes the form of a distorted black / white checker board, with about the same number of squares on a side. Sometimes the black and white portions exchange places, quite rapidly. I don't know how to induce it, but I have experienced it a few times. It was actually quite a shock to see it in a physical form.

  4. Very cool.

    I assume you above used an actual ruler held up against the screen?

    Use “Free Ruler” on the Mac, or one I wrote for the PC a long time ago, and compare pixels to pixels. The lines are in fact all straight. The ruler image appears to acquire a bulge or a waist, depending on where you place it. But you can get it to where the line is one pixel away from the ruler edge, and use a magnifier (zoomin on the PC, or I grabbed it into an image file and used Preview on the Mac to enlarge it) to examine the edge for proof.

    You may have either a bent ruler, a bent screen, imperfections in the pixel array on the screen, or your eyes are still affected and the gap between the ruler and the screen allows more of the illusion through than you think.

    This particular image is playing off something the optical nervous system does anyway – there is one particular after-image / fill-the-dark that sometimes can be experienced which takes the form of a distorted black / white checker board, with about the same number of squares on a side. Sometimes the black and white portions exchange places, quite rapidly. I don’t know how to induce it, but I have experienced it a few times. It was actually quite a shock to see it in a physical form.

  5. @Gray Gaffer,

    Yep, against an actual steel ruler, checked against reference sample for straightness as well. Screen tests fine (double-checked). I just got new glasses a couple of months ago, and I don't suffer from astigmatism (which would cause the same effect) either. Something's not kosher in Switzerland.

  6. @Gray Gaffer,
    Yep, against an actual steel ruler, checked against reference sample for straightness as well. Screen tests fine (double-checked). I just got new glasses a couple of months ago, and I don’t suffer from astigmatism (which would cause the same effect) either. Something’s not kosher in Switzerland.

  7. Forgot to mention also that other straight lines on the same screen do, in fact register against that same ruler as straight lines, just not the ones in the center of the 'illusion.' Hmmm…

  8. Forgot to mention also that other straight lines on the same screen do, in fact register against that same ruler as straight lines, just not the ones in the center of the ‘illusion.’ Hmmm…

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