Video Illusions

By Phil Plait | July 10, 2010 7:30 am

I love optical illusions, and I’m fascinated by the mechanics of vision, so I have to share with you this video. This technique of animation has been known for a long time, but it’s still pretty cool.

Another video discusses how this is done. I had a card I carried in my wallet for years that did a similar type of illusion using a lenticular overlay which, when you moved the card back and forth, made it look like little colored spirals were rotating in different directions. I bought it when I was in college, but sadly I lost it last year (I’m pretty sure I dropped it at Comic Con). I have no idea how to replace it. If any of you has seen something like it, please let me know!

Tip o’ the Fresnel lens to BABLoggee Cristiana Senni.

MORE ABOUT: optical illusion

Comments (24)


    Phil Plait:

    I bought it when I was in college, but sadly I lost it last year (I’m pretty sure I dropped it at Comic Con).

    Most likely that the person who ‘accidentally’ bumped into you there probably pinched it!

  2. Nifty little trick there! I wonder if kinda the same illusory effect is at play in a different form when it comes to religion. The human brain seems rather easily deceived into convincing itself that things that aren’t really there are, after all.

  3. KurtMac

    There is an entire series of children’s books featuring this, the first of which is called Gallop!

  4. In the 1980s, when I was at school in Scotland we went on a trip to visit the Loch Awe / Ben Cruachan pumped storage power station (well worth a visit if you’re in the vicinity).

    The visitor centre was full of big back-lit colour diagrams and schematics. They used the same trick to show ripples along the pipes indicating direction of water flow. It was extremely effective, probably quite cheap, and I’ve never seen it in use anywhere else.

  5. @KurtMac I was just about to post the same link. I had one of these for my kids. It’s great: the images move as you turn the pages. The author also does murals.

    …and completely unsurprisingly, there’s an Instructable on how to make your own.

  6. Phil, I don’t think these tricks can be called illusions. Illusions, like the parallel lines that seem to be bent, play on the strangenesses in the eye’s connection to the brain, while those rotating gears are no more illusory than the motion in movies.

  7. HvP

    Ahhh, Jonathan,

    But the effect used to produce movies is an illusion as well. It’s really just a series of still pictures that aren’t moving on the screen at all. Movies take advantage of your brain’s “persistence of vision” to make it seem like the images are moving. They just play so quickly that your brain doesn’t notice the gaps.

    In that sense, these are illusions as well. There are no gears there, and they aren’t spinning. Your brain is ignoring the “gaps”, the spacers that hide the fact that they aren’t complete gears.

  8. Austin

    The one with the gears is my favorite.

  9. Nathan

    Where can you buy something like that?
    My nephews would love it.

  10. Speaking of movies, this is how the “Krel Shuttle Car” scene in “Forbidden Planet” was done, except the grid was rotating rather than linear. Same principle, though.

    – Jack

  11. reidh

    isn’t there about a half a million sites with this on them?

  12. Chris

    of course, this kind of animation has little to do with the mechanics of vision… You just see part of the backdrop at a time, since the rest is masked.

  13. CB

    I enjoyed this, thank you, and I enjoy optical illusions, but I have to agree with Jonathan #7 that these are strictly speaking animations and not what we expect as optical illusions. I disagree with HvP #8 that the term optical illusion applies to any animation. Various ways of doing animation present a series of frames to the eye that we interpret as motion. These are all animations and not optical illusions. With an optical illusions we expect to see the same color that appears different in different contexts, straight lines that look crooked, etc. I had never seen this exact effect before and it was cool, and I appreciate the post, but I don’t think animated optical illusion is quite the right title for it.

  14. Tobin Dax

    Would these be illusions instead of animations if they showed static images? Instead of a rotating cube, what if only one cube image was drawn, and it could only be seen when the overlay was placed with its gaps in the right place?
    Why is that different than your brain bending straight lines?
    Why is it no longer an illusion if it is possible to see more than one object or more than one orientation?

    (Edit: Let me clarify the first question: Would these be illusions if each showed only a single, static image?)

  15. disciple of "Bob"

    I demand to know the composer and title of the music; I am going to eat cold spaghetti in protest until my demands are met.

  16. It would cool to scale this up and paint designs on the walls of subway tunnels that appear to animate themselves when viewed through the windows of a moving train.

    Passengers could enjoy an amazing show!

  17. sylva333

    They do! I saw it in DC, it was really cool.

    Here’s an advertisement for Target in the DC subway:

    Here is a video of a movie advertisement on a subway:

    Here’s a cool Microsoft advedrtisement that looks more like an animation:

    This is a cool one in Kiev:

    This my favorite that I found, it’s just shapes and boxes, I think this one is really art rather than a system that is more like video that they can change easily:

  18. Cool. Someone mentioned the Gallop book – if you like those, there’s a whole series called Scanimation books (they even have a Star Wars Scanimation book…).
    I came across this on deviantArt, they have some neat optical illusions and OpArt stuff:

  19. Pi-needles

    @16. disciple of “Bob” Says:

    I demand to know the composer and title of the music; I am going to eat cold spaghetti in protest until my demands are met.

    Have you exploded from continuously eating cold sphaghetti yet? ūüėČ

    Sorry I don’t know. :-(

  20. Oana S.

    Great stuff! Animations like that just make you realise how you can be tricked even though you know it ūüėõ

    @sylva333 That is awesome stuff! My favorite is the one in Kiev. There was one in the Bucharest subway for Coca Cola. Couldn’t find the video. I think they are an effective advertising channel. People usually complain that in the subway there’s nothing to see out the window :) They don’t seem to have caught advertisers’ attention though…

  21. Robert Carnegie

    Have you seen the “Rotating Snakes” images, which seem to squirm or flow when in fact they’re completely still?

    I think it partly depends on the bright colours of a computer monitor (where of course you may really see moving images, too), but you can also do it on paper. is one collection of several different effects, maybe including yours.

  22. Rob

    I am not sure if this is the type of lenticular lens that you were refering to, but there is a pocket magic trick called Reality Twister, that might be along the lines of what you were talking about…just a thought…

  23. Rob

    My wife’s grandfather was an artist/photographer/musician of some note in early 20th century Florence. Among his works is a small, roughly 2″ x 4″ blurry photo of his wife on which, when the observer moves a diffraction grating in front, the image winks and smiles. It’s definitely not an illusion but more akin to the original experiments in movies, like Muybridge’s photo studies of horses galloping.


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