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By on October 5, 2011, with 72 Comments

Tilted Road Optical IllusionSome time ago, Karthik has sent me this illusion of two parallel airplane tracks. Even though I checked over and over again, I can’t seem to comprehend these are two identical photos lined one next to each other. Why is this happening? What causes us to see the right track heavily tilted when compared to the left track? I realize we had few similar illusions before, yet what is happening here I can’t understand.

I also noticed one particular comment from few days back, suggesting I should allow you to rate posts from the homepage as well. Up until now, you were allowed to rate illusions only from inside the particular post. The reason I excluded homepage lyes in the fact that many of our posts are cut-off on the homepage. Many articles contain more than one photo, where only first one is visible on the starting page. Still, I tweaked the ratings so from now on you should also be able to vote from the homepage. Let’s see how this turns out…

Comments

72 Responses
  1. EngrDude says:

    I believe the illusion is a result of the lines parallel to the runway in the photo. Back in high-school Art class we spent a week on perspective and learned that everything must go back to a central point on the horizon. You’ll notice that the sides of the runway and all of the lines parallel to it seem to be getting smaller in the distance and if you were to continue those lines off of the top of the page they would all intersect at some point. Now the illusion comes in when you put those the image next to itself as we have here, your brain is convinced that one runway is running straight up the page (for me it was actually the right side) so when the lines from the images intersect the common edge at an angle, your brain exaggerates the angle to causing the other image to appear slanted. Test: cover one side with your hand, then cover the other with your hand, when you only see one image the runway is always straight.

  2. Adam says:

    They dont look parallel because they are taken from the same perspective.

  3. Josh says:

    This illusion makes my brain cook. Great!

  4. yeda says:

    What’s happening here is that the brain thinks, this is one big picture. But if this was one picture, both airplane tracks should have the same vanishing point in the distance, if they were parallel.

    So the brain deduces, that the tracks must be skewed to make up for this.

  5. JuniorJedi says:

    This is also a stereogram. If you let your eyes diverge (as if you’re looking at something in the distance) you’ll see 3 images. The one in the middle has a definite 3D effect.

    • Jules the Geographer says:

      Actually this is a pseudostereogram, you dont get a true 3D effect only that the central image is raised compared to the two images individually. to get a true stereogram out of this the perspective would have to be slightly shifter between images.

  6. Yannick says:

    I don’t know why his this happening, but i notice that if you move your point of view from left to right, you notice that the tilted track change side

  7. LDB says:

    Tilting your monitor to the far left and right “fixes” the parallelism as well.

  8. cletus says:

    I didn’t believe my eyes so I copied the left runway and pasted it to the right of the right runway such that I had 3 runways. Now the copy on the right seems to be tilted more than either of the other two!

  9. lee says:

    Hello, are you aware of the effect of stereoscopic 3D? it is a technique that puts two almost identical images next to one another and if you cross your eyes just enough the two 2d images focus to form one 3d image. I know its got nothing to do with the illusion displayed here except that it can be used to show the two images are identical as they overlap perfectly.

  10. DANIBIRD says:

    I THINK YOU MEAN TILTED!!! I READ IT AS TITLED AND DID NOT UNDERSTAND U AT FIRST. BUT YES COMPLETE MADNESS IT TILTS TO THE RIGHT.

  11. Paul says:

    Compare the hash-marks in the lower right corner. It appears (no pun intended) that the angle of the photo is off — indicating two photo’s; or at least the illusion comes from one runway being slightly off-center in it’s photo.Just that slight deviation could be enough to confuse the brain(?).

    • Wilson says:

      They aren´t the “same” images. The right´s photo is a bit shifted to right. I think that´s enough to cause the illusion.
      You can Split the two images in two files and use a image viewer. (I’ve used Irfan view)

      Anyway, that´s awesome !!

  12. DFrsk says:

    very strange!

    keep up the good work on this page

  13. Kimon says:

    Both runways are slightly tilted to the right. So their far ends are not equal distance from the middle border.

    The trick comes from the brain treating it as a single image and assuming a single viewing point in the centre at the bottom. If you draw lines extending radially from that point, symmetrically on either side of the middle border, you’ll see why your depth perception tells you the right runway is more tilted.

  14. yusuf O says:

    This is amazing…!!
    I Actually took a printout and overlapped it beneath the light but couldn’t find an image tampering…
    good stuff…

  15. Aron Rubin says:

    This is actually a scene that is used to illustrate the difference in anisotrophic filtering used in 3d rendering:

    http://en.wikipedia.org/wiki/Anisotropic_filtering

  16. chris says:

    It looks like two different photos to my eyes.
    The second taken at a slightly different angle
    than the other. It looks as though the second is taken turned a little to the left.

  17. Code Monkey says:

    I have a buddy of mine who has eye problems, preventing him from focusing properly in some cases. I showed him this illusion and he asked me “What’s wrong with it? They look exactly the same to me.”

    *boggles*

    • Monte says:

      If you squint or blur your eyes a little and imagine the runways as being, say, two tall black Kachina dolls with white feet standing in front of a rock wall they appear standing or leaning the identical tilt.

  18. Hink says:

    the real illusion is the delusion that this RUNWAY is a road lol…sorry couldn’t resist

  19. Conrad says:

    neat Illusion

  20. spartacus says:

    For anybody thinking the two images might be different, this animation should put your mind at rest
    10.gif

  21. Pygormus says:

    I thought I was wrong until I saw that others had made the same observation, namely that the two images are NOT identical. If they were, they wouldn’t form a stereoscopic (not stereographic) image. In other words, the image on the right does “tilt” a bit.

  22. Henri says:

    Parallel lines appear to meet at the vanishing point. If this was one picture of two parallel runways, they would both point at a point between the two. Since it is two pictures next to each other, each runway has its own vanishing point so your brain, in trying to make them into one picture, tells you that they are not parallel.

  23. Dave says:

    I think this is fascinating. I must only guess that the image on the right is tilted because of the way the photograph is cropped. I want to say that in the original photograph, the amount of space to the left of the runway is greater than the amount of space to the right. I think the terrain is also similar in composition.

    When the identical photos are placed next to each other, because of the similar terrain and additional space created in-between, the “once greater” space to the left of the runway becomes even more so for the runway on the right, making it seem to lean further.

    Just a hypothesis, It would be interesting to know what sort of scientist one would ask about this. Optical Psychologist? Hmmm

    What ever the answer, it’s a cool effect.

  24. Ron C says:

    First, this isn’t two photos. It is one photo, duplicated and laid next to each other.

    If you cover the left photo The tilt of the right photo disappears. Just being curious, what would it looked liked if you place 10 photo next to each other. would the nine on the right lean? Also, why is the run way leaning to the right and not the left?

  25. Dolphin says:

    Nice.It’s interesting how our minds perceive things,isn’t it?

  26. Kelsey says:

    If you use a new version of the firefox browser, you can actually click on the picture nad move a “shadow” copy across so that it’s over the other half. This proves that the two halves of the image are identical.

    I don’t see how two identical pictures could make a stereoscopic 3d picture, as the 3d effect comes from slight differences in the images (which aren’t there).

  27. Chris says:

    Actually, it is a stereoscopic image ;)
    If you cross your eyes, it will become another great 3D picture :D

  28. Ben says:

    I learned this in an art class. Your brain naturally compares an object to it’s surroundings when determining an angle. This is why a line by itself cannot be perceived as slanted even if it is and why one road is perceived as slanted. The angle of the lines on the right side of the left picture (and the reverse as well) are tricking your brain. Tile the image a third time and you’ll see what I mean.

  29. Stanley says:

    Enjoy your site. The illusions are great so keep them coming. ignore the haters. I have spent over 4 years trying to learn spanish and I still have difficulty writing it properly.

  30. Alan p-j says:

    since when does viewing the same thing from 2 different angles make an illusion?
    Someone, please explain. After all a runway is a runway is a ru…..

  31. robert says:

    I agree with earlier comments that this is a stereogram. It’s likely designed to go in one of those old fashioned eye scopes where you place the card in and out comes a 3D image. You can get this effect by looking at your screen and crossing your eyes. As they uncross, watch intently the numbers and hash marks at the bottom of the runway. Your eyes should reach a point where the numbers go into perfect sync and then you can look up the picture to see a perfectly straight runway. It’s not quite as exciting as some as it lacks anything like planes, or a terminal to give it true 3D pop-out, but it’s still nicely done.

  32. benua says:

    I think it’s because of the point of view of the original picture that give a strong perspective to the road. If you compare the edges of the road (withe lines) they seems parallel.

  33. Saul says:

    Hi,

    In my perception, I think that, the images they are not
    at the same angle, take attencion on the right picture on is left side, if you see closer you can see at least two different aspects.

  34. bill says:

    I dont see any tilt

  35. Eddie says:

    Any artist who knows about perspective and vanishing points would tell you that these are simply two photos next to each other and not two airstrips next to each other.

  36. tuxedomoon says:

    excellent!!!
    this one is still making my brain burn!

  37. Joe Black says:

    They are pictures of the same runway from different angles. If the two pictures were cut and lined up straight they would look identical. It’s in the cropping not the picture.

  38. Joe Black says:

    People it is the same runway, they have the same ID, 28L. First, if they were two separate runways, they would not be that close, and second, one would be 28L and one would be 28R. If they were both 28 they would have to be parallel, because that refers to the degrees on a compass, “36″ being North and “18″ Being South. 28 would be one degree above due West. This picture is cocked, not the runway.

  39. Scott says:

    I don’t think they are identical. Yes, they’re exactly the same image, but if you look closely at the left image, there appears to be 3, maybe 4 pixels that have been coppied and placed along the right edge of the image to extend that image just a few pixels farther. If you look at the runway, it’s not 100% vertical in the frame either, it tilts slightly to the right.

    I have verified this in image editing software and I encourage you to do the same thing. The severe tilt that we are seeing in the right image is most probably created by the extension of the left image’s right edge. It makes it seem like the left image’s runway is several pixels closer to the frame at it’s farthest point. This doesn’t make a big difference up close, but because our minds are able to comprehend distances and proportion, the difference is much more obvious at the runway’s farthest point.

  40. Scott says:

    Edit:
    It makes it seem like the left image’s runway is several pixels **further** from the frame…

  41. Joe Smith says:

    i rotated image 180 deg. and the run way on left looks skewed to me.

  42. Scott says:

    www.http://biohazardgfx.com/OpticalIllusionFix.jpg/img

    I added the same 3 pixel offset to the right image. Can you see the difference?

  43. ThIrD says:

    I can see the secret of this image! The two pictures are just the same and the lines of the two runways are parallel. Test yourself. When looking at the Image, move your head left and right while facing the two pictures and looking at them. so does it make sense!?

  44. lord ra says:

    this is just a stereogram, this illusion happens with most stereagrams. the two images here are infact different but only slightly, you can look at this in “3d” if you cross your eyes. evidence for the difference and the stereo are in the left side and right side of both images. ther stop at different points. this is hard to see on the small image. i think the illusion comes from the fact that the one image has a defined border and our brain can easyly determine that border but the next image across does not, so thi distance to the border from the runway appears larger. dont belive me, take your own steregrams (google it) with yoru iphone or what ever and experiment.

    • lord ra says:

      infact i would say he has been playing microsoft flight sim with a 3d driver and has taken a screen shot, he has doctord this pic to try and fool you as well, although this illusion happens regardless. but if you look closly at the right side of the left image you can see hes droubled up about 15 pixels worth. i think this is to confuse you when you try compare it with the right image to see if they are the same, but the left side of the image clearly shows about 5 pixels worth less of image then the right image. blatent steregram, sterescopy, 3d picture. ihave been doing my own stereo photos and video for well over 10 years now and i have seen this many times

  45. Tdawg says:

    The point in which the runways disappear into is known as the vanishing point. When there is two like this one, the vanishing point is not correct. This is a copy of two pictures. If there is more than one vanishing point then they would be on the sides not at the tops which is where we get our depth perception.

  46. Care Bear says:

    I see this sort of thing all the time if my eyeballs happen to be acting independently and if I’ve been driving too long.

  47. Pam says:

    I don’t see a tilt in the roads, they just look like the same picture next to each other, ah well hehe

  48. lasz says:

    I think it is because your brain treats the two images as one.

    one of the two pictures is used by your brain as a “reference-perspective”.

    say we take the perspective of the left picture as our “reference”.

    If the right airplane track would exist in the perspective of the left one, those tracks would actually diverge in real life.

    hope this makes sense

  49. Oron says:

    Awesome illusion! Rather than *parallel* runways, they are two copies of the same runway, which makes the illusion even more amazing! In my opinion, the illusion is caused by the perspective lines of the runway moving diagonally towards a convergence point. What our brain perceives is primarily the angle between the two adjacent lines (the left side of the picture on the right, and the right side of the picture on the left), giving the impression that the whole runway is going in a different direction.

  50. drcrypto says:

    Even more of an illusion than you thought.

    Treat this like a 3D picture. Let your eyes cross and you get a runway straight as an arrow right up the middle with the original runways on each side. 3 runways in total.

  51. Bill says:

    The reason you are percieving the right strip as being slanted is due to the space between the strips in the two images. On the left image, you have a small section before you hit the white space at the edge of the image where internally you summarize the angle- on the right image you not only have that space, but also the space to the left of the original photo giving the illusion that there is more space so more of an angle since your mind has already summarized that the left track is relatively straight. The cool thing, if you focus on the right track and move left you will find the left track is more angled- this may be harder for some since we are taught to look left to right.

    • FathomSavvy says:

      @Bill Neither tracks are angled. They both point exactly “North”. I don’t know the answer, but I think it’s called parallax. It could also be that one eye is “stronger” than the other. There is an answer out on the web for this phenomena, I just don’t know it. Both pics are exactly equal.

  52. Shanna says:

    I can see that on the upper-middle left side of the right picture, there is a semi-circle formed by a road around a piece of land, the right picture has more land. It is just a little but enough to make a difference in the angle. Love this site though. Much Fun!

  53. isaac says:

    This one fooled me for a bit, but after about a minute of pure frustration I realized why I couldn’t comprehend the parallelism of the 2 pictures. I was comparing the right edge of the left road and the left edge of the right road. If you look at either the left or right edge on both roads, it becomes immediately obvious they are the same picture. Simple, but a devious illusion nonetheless. Bravo, Mr. OP.

  54. Jay says:

    I can’t make these look parallel. Measuring distances shows that they actually are, but I can’t force my eyes to agree, regardless of how I isolate my view. Very nice illusion.

  55. Fred says:

    Tracks? Trains use tracks. That is a RUNWAY, the place where aircraft leave and to where, barring unforeseen circumstances, they return.

    WHITE SPACE? What white space?

    • Kirk says:

      I tried for 2 minutes to figure out WTH the writer was talking about when she called them “airplane tracks” so I scrolled down, hoping that I was not the crazy one here because I could not see the so-called “tracks.” I saw your comment and I knew that I was NOT crazy, and we seem to be the only ones so far who know that these are photos of one runway, 28 Left.

  56. Jan Gutbayer says:

    it creates 3D illusion when you look at it as on the stereoscopic image (like those “grainy” pictures that become 3D when you look at them crosseyed). It’s cool…

  57. Lonnell says:

    WEll if you look closely the picture is the same however the picture on the right seems to have been slightly pushed over. For example there is a little white line in the bottom left hand corner of both pictures however on the picture on the right there is a little more space between that line and the end of the picture.

  58. Allie says:

    Here’s what’s going on.

    Every thing has a vanishing point. This is where all the parallel lines come to meet at a single point in the distance. Example: when you’re driving and the road you’re on looks widest where you are and very skinny off to where you’re about to go. Of course, you get there, and it’s the same width.

    So we look at the picture on the left and see the run way meeting off in the distance. The picture next to it, although the same picture, has a different vanishing point all to itself. We look at the pictures together and want them to converge at the same point above the left runway, but they don’t, so it looks tilted.

    SCIENCE!

    learn more here:
    http://en.wikipedia.org/wiki/Vanishing_point

  59. mike g says:

    Interesting. If you try to line the photos up with your eyes, so that your nose is directly in between the two photos, and alternately blink your eyes, it seems as if the runway on the left is straight when looking at it with your left eye, while the runway on the right tilts off. Then it switches when just using your right eye. Each eye seems to be independently “seeing” the pair angled differently.

  60. mike says:

    This is no illusion. The photos are not the same.. the hash marks in the right picture or not centered like the photo on the right.. this was taken from a camera that was shooting multiple shots per second and the picture on the right even though close to the same vantage point was definitly shot after photo on the left giving you this illusion it was taken from an airplane or a helicopter sweeping left to right across runway

  61. David says:

    I would wager if this were to be viewed by someone in a culture that reads right to left, the leftmost photo would be the one that appears tilted. We, in the west, tend to use the left as our anchor point and what follows then relates to that anchor.

    Any native readers of Hebrew out there who might confirm or deny this?

  62. Not Me says:

    The two image are NOT in fact identical. Look for and observe the small details in the edges of the images. Observe their distances from the egdes or even their appearances at all. Their is proof they are not identical. I am not, however, denying the illusion created here. But I am stating that some deceit was involved.

  63. Link the Hylian says:

    If you look at the bottom left of each picture, the left side has a shadow starting from it’s edge, whereas the right picture has that same shadow running perpendicular to the left border and then start it’s ascent. And then look at the right side of each photo, you’ll notice the same. The left photo has a sliver of the left border cut off and the right photo has a sliver of the right border cut off, therefore offcentering the runway in each picture and giving a total variance of double the initial piece cut off. This picture is an optical illusion but does not state the truth of it’s nature.
    Try and take the left photograph and duplicate it yourself side by side, you will not end up with the same mental image that this photo is doing to you. I do also feel that the image on the right is slightly skewed by about 3 degrees, when I used Adobe’s photoshop it appeared about that much, but I can’t say exactly to what degree

  64. Gofirit80686 says:

    Ok, not understanding while some think this is fake. If you layer the right image over the left image and set opacity to 50% you will see they are identical. It is an illusion. Fact.

  65. Clint says:

    I think the brain reads from left to right therefore anything after something the brain will try and fore-read/see. now because there isnt anything after the right image the brain will concentrate on what is current. if you looked at the left imaghe the brain tries to fore-read/sea the right image hence blocking out a few specifications that you will see if you bliocked out the right picture….

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