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You can also clearly see the lines getting sharper near the sphere, as well as bending because part of the blurred image is blocked by the sphere.

In fact, with my mild (about −1 dpt) myopia, I can personally confirm that, without my glasses, I can easily see both the bending effect and the sharpening of background features when I move my finger in front of my eye. I can even see a hint of astigmatism (which I know I have; my glasses have some cylindrical correction to fix it) in the fact that, in some orientations, I can see the background features bending not just away from my finger, but also slightly sideways. With my glasses on, these effects almost but not quite disappear, suggesting that my current prescription maybe just a little bit off.

You can also clearly see the lines getting sharper near the sphere, as well as bending, because part of the blurred image is blocked by the sphere.

In fact, with my mild (about −1 dpt) myopia, I can personally confirm that, without my glasses, I can easily see both the bending effect and the sharpening of background features when I move my finger in front of my eye. I can even see a hint of astigmatism (which I know I have; my glasses have some cylindrical correction to fix it) in the fact that, in some orientations, I can see the background features bending not just away from my finger, but also slightly sideways. With my glasses on, these effects almost but not quite disappear, suggesting that my current prescription may be just a little bit off.

You can also clearly see the lines getting sharper near the sphere, as well as bending, because part of the blurred image is blocked by the sphere.

To recap: This effect is caused by the background being (slightly) out of focus, and by the foreground object effectively occluding part of the camera  / eye aperture, causing the effective aperture (and thus the resulting image) to be shifted. It is not caused by:

• Diffraction: As shown by the computer renderings above (which are created using ray tracing, and therefore do not model any diffraction effects), this effect is fully explained by classical ray optics. In any case, diffraction cannot explain the background images shifting towards the obstacle when the focus is behind the background plane.

• Reflection: Again, no reflection of the background from the obstacle surface is required to explain this effect. In fact, in the computer renderings above, the yellow sphere  / cylinder does not reflect the background grid at all. (The surfaces have no specular reflection component, and no indirect diffuse illumination effects are included in the lighting model.)

• Optical illusion: The fact that this is not a perceptual illusion should be obvious from the fact that the effect can be photographed, and the distortion measured from the photos, but the fact that it can also be reproduced by computer rendering further confirms this.

Addendum: Just to check, I went and replicated the renderings above using my old dSLR camera (and an LCD monitor, a yellow plastic spice jar cap and some thread to hang it from):

In fact, with my mild (about −1 dpt) myopia, I can personally confirm that, without my glasses, I can easily see both the bending effect and the sharpening of background features when I move my finger in front of my eye. I can even see a hint of astigmatism (which I know I have; my glasses have some cylindrical correction to fix it) in the fact that, in some orientations, I can see the background features bending not just away from my finger, but also slightly sideways. With my glasses on, these effects almost but not quite disappear, suggesting that my current prescription may be just a little bit off.

You can also clearly see the lines getting sharper near the sphere, as well as bending because part of the blurred image is blocked by the sphere.

To recap: This effect is caused by the background being (slightly) out of focus, and by the foreground object effectively occluding part of the camera/eye aperture, causing the effective aperture (and thus the resulting image) to be shifted. It is not caused by:

• Diffraction: As shown by the computer renderings above (which are created using ray tracing, and therefore do not model any diffraction effects), this effect is fully explained by classical ray optics. In any case, diffraction cannot explain the background images shifting towards the obstacle when the focus is behind the background plane.

• Reflection: Again, no reflection of the background from the obstacle surface is required to explain this effect. In fact, in the computer renderings above, the yellow sphere/cylinder does not reflect the background grid at all. (The surfaces have no specular reflection component, and no indirect diffuse illumination effects are included in the lighting model.)

• Optical illusion: The fact that this is not a perceptual illusion should be obvious from the fact that the effect can be photographed, and the distortion measured from the photos, but the fact that it can also be reproduced by computer rendering further confirms this.

Addendum: Just to check, I went and replicated the renderings above using my old DSLR camera (and an LCD monitor, a yellow plastic spice jar cap, and some thread to hang it from):

In fact, with my mild (about −1 dpt) myopia, I can personally confirm that, without my glasses, I can easily see both the bending effect and the sharpening of background features when I move my finger in front of my eye. I can even see a hint of astigmatism (which I know I have; my glasses have some cylindrical correction to fix it) in the fact that, in some orientations, I can see the background features bending not just away from my finger, but also slightly sideways. With my glasses on, these effects almost but not quite disappear, suggesting that my current prescription maybe just a little bit off.

Above, you can see two renderings of a classic computer graphics scene: a yellow sphere in front of a grid plane. The image on the left is rendered with a narrow aperture, showing both the grid and the sphere in sharp detail, while the one on the right is rendered with a wide aperture, but with the grid still perfectly in focus. In neither case does the effect occur, since the background is in focus.

Things change, however, once the focus is moved slightly. In the image on the left below, the camera is focused slightly in front of the background plane, while in the image on the right, it is focused slightly behind the plane:

I can even recreate the broken line effect in your photos by replacing the sphere with a narrow cylinder:

The photo above on the left has the camera focus behind the screen, the one on the right has it in front of the screen. The photo below on the left shows what the scene looks like with the screen in focus (or as close as I could get it with manual focus adjustment). Finally, the crappy cellphone camera picture below on the right shows the setup used to take the other three photos.

Above, you can see two renderings of a classic computer graphics scene: a yellow sphere in front of a grid plane. The first image is rendered with a narrow aperture, showing both the grid and the sphere in sharp detail, while the second one is rendered with a wide aperture, but with the grid still perfectly in focus. In neither case does the effect occur, since the background is in focus.

Things change, however, once the focus is moved slightly. In the first image below, the camera is focused slightly in front of the background plane, while in the second image, it is focused slightly behind the plane:

I can even re-create the broken line effect in your photos by replacing the sphere with a narrow cylinder:

The first photo above has the camera focus behind the screen; the second one has it in front of the screen. The first photo below shows what the scene looks like with the screen in focus (or as close as I could get it with manual focus adjustment). Finally, the crappy cellphone camera picture below (second) shows the setup used to take the other three photos.