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fun optical illusion

Discussion in 'General Discussions' started by Hugh Jarss, 2007/12/09.

  1. 2007/12/09
    Hugh Jarss

    Hugh Jarss Inactive Thread Starter

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    Hugh Jarss,
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  2. 2007/12/09
    BillyBob Lifetime Subscription

    BillyBob Inactive

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    Thanks for the fun.

    Worked very well for me too.

    BillyBob
     
    BillyBob,
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  4. 2007/12/10
    AceH

    AceH Inactive

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    Works for me also.
    I'm going to give my brain a "time out" for being so easily fooled. :D
     
    AceH,
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  5. 2007/12/10
    Christer

    Christer Geek Member Staff

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    It seems to be on a "per eye" basis. Close one eye and focus on the + and when the red dots are gone, open both eyes!

    Christer
     
    Christer,
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  6. 2007/12/10
    Evan Omo

    Evan Omo Computer Support Technician Staff

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    That was very interesting how your brain can be fooled so easily. :rolleyes:
     
    Evan Omo,
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  7. 2007/12/10
    Ka2mxh

    Ka2mxh Inactive

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  8. 2007/12/10
    Hugh Jarss

    Hugh Jarss Inactive Thread Starter

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    Christer,

    you've got me sitting here with a piece of card with a hole in it in one hand, and the other hand "ready to go" in shutter mode (keeping both eyes on the cross thingy in the middle to make it a fair test) performing a kind of inverted semaphore... must look quite barmy ;) (no change there then) trying to see whether you're right... and yes, indeed it does seem to work per eye. Nice one!

    best wishes all, HJ.
     
    Last edited: 2007/12/10
    Hugh Jarss,
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  9. 2007/12/10
    Christer

    Christer Geek Member Staff

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    HJ,
    the question is whether the brain or the eye is tricked? Could be either since each eye has its own little "spot" in the brain (I think).

    What happens may be similar to not seeing everything clearly using the peripheral vision (the eye can only focus straight ahead) but moving objects are seen. I read the text to the left and noticed that I only saw the moving green dot, not the stationary red ones, using my peripheral vision.

    Another question is why the moving dot turns green? "Opposite colours" or something like that?

    Christer
     
    Christer,
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  10. 2007/12/10
    Hugh Jarss

    Hugh Jarss Inactive Thread Starter

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    magenta and green are indeed opposite, so seeing "sudden lack of magenta" might well expected to produce green (his dots are #fe0afe in the middle);

    cyan -> red should also work and seems to, although perhaps not as convincingly as magenta -> green; peripheral vision's good! The illusion seems to work best for me about the same distance off-centre as the blind spot but on the opposite side. I get a good "red" dot like this, but the cyan won't "vanish" as efficiently as the magenta does - perhaps because there's a greater difference in brightness between red and cyan, than there is between green and magenta?

    (Y=0.59G + 0.30R + 0.11B from old colour TV reference manual)(so Mg:Gn = 0.41:0.59, but Cy:Rd = 0.70:0.30, so much more brightness flicker)

    (ideally I suppose one would want these as close to equal as possible, and of the same luminance as the surrounding grey?)

    fuzzing the edges of the dots is probably crucial to getting it to work well!

    ==

    eye or brain? I really don't know! And does the timing matter?

    Which makes me wonder: when something comes towards your eyes and you blink, it's really really fast - much quicker than a "normal" human reaction time. (thank goodness). Does that actually get as far as the brain and back? - or is there some "local" processing going on in the eye itself?

    best wishes, HJ.
     
    Hugh Jarss,
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  11. 2007/12/10
    noahdfear

    noahdfear Inactive

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    Focus on 1 pink dot long enough and you will see only the geen dot rotating.

    Now cover 1 dot with a peice of paper that you can see the dot through, then focus on that dot until you see only the green rotating dot ........ plus the pink one behind the paper!
     
    noahdfear,
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  12. 2007/12/11
    Christer

    Christer Geek Member Staff

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    HJ,
    cyan -> red doesn't work that well for me. Some dots disappear but all have not (yet) disappeared at the same time and they "disappear and come back only to disappear again ". Keeping a steady focus is important. If I change the focus the slightest, the dots come back. Not so sensitive with magenta -> green.

    noahdfear,
    it seems like you can focus almost anywhere as long as you have something to focus on. I don't have any transparent paper so I can't try that one.

    This is probably not as simple as we are trying to make it. The magenta dots do not move or rotate clockwise. They are "turned off and on" in clockwise order. When a dot is turned off, its opposite color appears in its place. Maybe the brain (or the eye) is considering the static dots to be of no importance and ignores them but the moving dot is worth tracking.

    I mentioned "a steady focus ". An eye that is moving in its socket can not focus. The eye doesn't "sweep" along a page when you read but it moves the focus in increments. In this illusion, we focus on a + and the peripheral vision plays tricks on us. I wonder if this would work on a huge screen and the viewer being far away, far enough to have the screen out of focal distance (eyes are not accommodating)?

    Christer
     
    Christer,
    #11

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