# What kind of optical illusion is this (pic in thread): **URL:** \ **Category:** Factual Questions\ **Created:** [March 2, 2012, 4:02pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555 "2012-03-02T16:02:24Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![standingwave](https://avatars.discourse-cdn.com/v4/letter/s/9de0a6/32.png) [@standingwave](https://boards.straightdope.com/u/standingwave)\ **Post date:** [March 2, 2012, 8:42pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/21 "2012-03-02T20:42:38Z")
> [@Bytegeist](#): > > He’s kind of funny-lookin’. > > More’n most people. In what way? Oh, just in a general kinda way. ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [March 2, 2012, 8:45pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/22 "2012-03-02T20:45:33Z")
> [@pulykamell](#): > > I don’t know about you, but for me, I find it extremely difficult to focus on the picture. My eyes keep fluttering back and forth between the two faces and it’s kind of making me feel like I’m drunk. My eyes or brain are trying to force the picture into single vision. Makes me feel like my glasses are on crooked, and my eyes are trying to adjust to line up the images. If my glasses are slightly crooked, each of my eyes seems to focus and move slightly independently until each image lines up correctly. Or, if that’s impossible, my brain seems to ignore my non-dominant eye. This “illusion” seems to trick my brain into thinking my eyes aren’t lined up properly, so my eyes are constantly adjusting their position and focus, independent of each other. But it’s even more disorienting since all those adjustments don’t actually change anything. For comparison, here is the [original](http://www.sadanduseless.com/wp-content/uploads/2011/04/steve-buscemi.jpg) (I hesitate to call it “normal”) version of the very same image. Those of you with glasses can try setting them crooked to see a similar effect. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [March 2, 2012, 11:53pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/23 "2012-03-02T23:53:30Z")
Ah, so the Thatcher effect is why I can spot a picture of a beautiful woman in a magazine, but then turn it right side up and change my assessment completely. I’ve always wanted to bring this up on the board before, but lacked an appropriate place. Still, the thing that fascinates me more is that, once you know what it looks like upside up, turn it upside down again, and you will not be able to not notice the flaws again. ---
**Author:** ![tanstaafl](https://avatars.discourse-cdn.com/v4/letter/t/ba8739/32.png) [@tanstaafl](https://boards.straightdope.com/u/tanstaafl)\ **Post date:** [March 3, 2012, 2:25pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/24 "2012-03-03T14:25:12Z")
> [@Hail\_Ants](#): > > That checkerboard & green cylinder illusion next to that paragraph totally blows my mind. When I first saw that a few years ago I was like, “What are they talking about? The two squares _ **are** _ different shades!” Liked it so much I made a T-shirt of it… Somebody made a [video of a real-life version of that one](http://www.youtube.com/watch?v=z9Sen1HTu5o). ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [March 3, 2012, 3:51pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/25 "2012-03-03T15:51:10Z")
> [@Hail\_Ants](#): > > That checkerboard & green cylinder illusion next to that paragraph totally blows my mind. When I first saw that a few years ago I was like, “What are they talking about? The two squares _ **are** _ different shades!” Liked it so much I made a T-shirt of it… Oh, I totally misunderstood that illusion. Based on how it was rendered in that Wikipedia article, I thought they were just talking about the orange dots (which, apparently is part of the illusion.) That’s the part I was less than impressed with. Now, the “white” and “grey” tiles actually being exactly the same color – that’s crazy. ---
**Author:** ![DCnDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dcndc/32/2842_2.png) [@DCnDC](https://boards.straightdope.com/u/DCnDC)\ **Post date:** [March 3, 2012, 4:19pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/26 "2012-03-03T16:19:11Z")
> [@pulykamell](#): > > Now, the “white” and “grey” tiles actually being exactly the same color – that’s crazy. If you cover the lit white tiles with your finger, it becomes obvious they are the same color. Take your fingers away, and they “magically” become completely different shades. Stupid brain! ---
**Author:** ![Mean\_Mr.Mustard](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mean_mr.mustard/32/3865_2.png) [@Mean\_Mr.Mustard](https://boards.straightdope.com/u/Mean_Mr.Mustard)\ **Post date:** [March 3, 2012, 5:37pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/27 "2012-03-03T17:37:54Z")
I believe that one’s called the Steve Bi-scemi. mmm ---
**Author:** ![shijinn](https://avatars.discourse-cdn.com/v4/letter/s/cc9497/32.png) [@shijinn](https://boards.straightdope.com/u/shijinn)\ **Post date:** [March 4, 2012, 12:09am UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/28 "2012-03-04T00:09:12Z")
> [@DCnDC](#): > > If you cover the lit white tiles with your finger, it becomes obvious they are the same color. Take your fingers away, and they “magically” become completely different shades. Stupid brain! the video is a good demonstration, you can _see_ it brighten up as the tile is moved into the shade.. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [March 4, 2012, 12:20am UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/29 "2012-03-04T00:20:38Z")
I don’t think the checkerboard “illusion” is an optical illusion. It’s a properly-functioning representation of tiles that _are_ the same shade _within that world_. They just happen to be shaded by an object within that world and their digital representation happens to be the same shade as some other tiles that had no shadow on them. That’s not an illusion, that’s our eyes working properly. ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [March 4, 2012, 1:08am UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/30 "2012-03-04T01:08:09Z")
> [@Ludovic](#): > > I don’t think the checkerboard “illusion” is an optical illusion. It’s a properly-functioning representation of tiles that _are_ the same shade _within that world_. They just happen to be shaded by an object within that world and their digital representation happens to be the same shade as some other tiles that had no shadow on them. > > That’s not an illusion, that’s our eyes working properly. What? ---
**Author:** ![coremelt](https://avatars.discourse-cdn.com/v4/letter/c/4491bb/32.png) [@coremelt](https://boards.straightdope.com/u/coremelt)\ **Post date:** [March 4, 2012, 2:09am UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/31 "2012-03-04T02:09:26Z")
wow I wonder if the double face illusion would still work in a video if you motion tracked the duplicate eyes and mouth. anyone seen an attempt at that? ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [March 4, 2012, 12:19pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/32 "2012-03-04T12:19:04Z")
> [@Reply](#): > > What? We could probably set up something similar in the real world if we had the proper shades calculated. Take tiles that are painted the same basic two colors and set them up so that half of them are in a shadow. Calculate the shadings needed so that the originally-lighter ones in shadow match the shade of the originally-darker ones in the light. Is this an optical illusion? ---
**Author:** ![shijinn](https://avatars.discourse-cdn.com/v4/letter/s/cc9497/32.png) [@shijinn](https://boards.straightdope.com/u/shijinn)\ **Post date:** [March 4, 2012, 12:36pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/33 "2012-03-04T12:36:25Z")
> [@tanstaafl](#): > > Somebody made a [video of a real-life version of that one](http://www.youtube.com/watch?v=z9Sen1HTu5o). > [@shijinn](#): > > the video is a good demonstration, you can _ **see** _ it brighten up as the tile is moved into the shade.. requoting link to the **VIDEO** of a physical recreation of the chequered shadow illusion; with spotlights, moveable tiles and everything. is it not remarkable that the same coloured tile appears brighter in the shade? ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [March 5, 2012, 12:41pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/34 "2012-03-05T12:41:33Z")
> [@tanstaafl](#): > > Somebody made a [video of a real-life version of that one](http://www.youtube.com/watch?v=z9Sen1HTu5o). That’s just silly. It’s impossible for it to work if there is an actual shadow being cast. The whole point of the illusion is that a white tile in shadow can be represented by the excat same shade as a grey tile in full light. Using video trickery with actual shadows is misleading. ---
**Author:** ![shijinn](https://avatars.discourse-cdn.com/v4/letter/s/cc9497/32.png) [@shijinn](https://boards.straightdope.com/u/shijinn)\ **Post date:** [March 5, 2012, 2:40pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/35 "2012-03-05T14:40:24Z")
i don’t get it. could you walk me through this? are you saying the video is photoshopped or something? despite the overhead spotlight, the shadow cast by the cylinder is real, right? ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [March 5, 2012, 3:07pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/36 "2012-03-05T15:07:24Z")
> [@shijinn](#): > > i don’t get it. could you walk me through this? are you saying the video is photoshopped or something? despite the overhead spotlight, the shadow cast by the cylinder is real, right? I don’t have the time to study the video and I don’t have sound, but the whole point is that _if there’s a genuine shadow_, then the colours can’t match. The illusion works in a still image because the colours and shadow intensity are such that the brightness of a light tile apparently in shadow is exactly the same as that of a dark tile apparently in bright light. If there was an actual shadow present, then the two tiles would have to be different colours. Because the brain sees one tile as being in shadow, it assumes that tile is lighter, hence the illusion. The video seems to be showing a dark tile in bright light appearing to be a light tile when it is moved into shadow. On rewatching the video, I assume the shadow of the cylinder is fake, because otherwise I don’t see how the illusion could work if there was a real shadow. ---
**Author:** ![shijinn](https://avatars.discourse-cdn.com/v4/letter/s/cc9497/32.png) [@shijinn](https://boards.straightdope.com/u/shijinn)\ **Post date:** [March 5, 2012, 3:48pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/37 "2012-03-05T15:48:25Z")
i see it now. thanks for pointing it out. :o ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [March 7, 2012, 6:59pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/38 "2012-03-07T18:59:16Z")
> [@Ludovic](#): > > We could probably set up something similar in the real world if we had the proper shades calculated. > > Take tiles that are painted the same basic two colors and set them up so that half of them are in a shadow. Calculate the shadings needed so that the originally-lighter ones in shadow match the shade of the originally-darker ones in the light. > > Is this an optical illusion? Yes, it is an illusion, and it shows how the brain interprets the raw data given to it by the eye. If you had that setup in real life, the two squares would be different colors, but due to the difference in the incident light they would appear identical to the eye, that is, the light reaching the eye is the same for both squares. However, the brain does a little post-processing and interprets what the color of the two squares would be if they were in the same light. The brain does the same thing when it sees the picture. Photographers know that what reaches the lens (or eye) is not just the absolute color of the object, but the amount of light being reflected back. You can make black look white if you shine enough light on it, and you can make white look black if it is in deep shadow. Next time you are watching a boring PowerPoint presentation at work, notice the areas on the slide that appear black. They are not really black, they are the color of the screen (or wall, or whatever you are projecting onto) which is usually white. If you turn the projector off, then the illusion of blackness is gone and you just see a blank white wall. But when there is the contrast of bright white light shining on other parts, the part with no direct light on it looks black. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [March 7, 2012, 7:39pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/39 "2012-03-07T19:39:02Z")
> [@Colophon](#): > > …_if there’s a genuine shadow_, then the colours can’t match. I agree. You can’t move a square into \*brighter \*light and have it look _darker_. I did frame grabs from this video, and in the setup, where they have the overlay saying that the two squares are the same color, [they really do appear to be the same color](http://www.seiglefamily.com/data/twosquares.jpg), although that’s not a big surprise. I still haven’t figured out what they’re doing when they move the square though, because the light setup looks as though it would render those shadows exactly as they appear. A spot behind the cylinder plus a soft box overhead would give the shadows that we seem to be seeing. Someone went to quite some trouble to produce this video, not entirely sure why. BTW, as far as sound, it’s just some New Age “massage” music. ---
**Author:** ![omos](https://avatars.discourse-cdn.com/v4/letter/o/e79b87/32.png) [@omos](https://boards.straightdope.com/u/omos)\ **Post date:** [March 7, 2012, 8:42pm UTC](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555/40 "2012-03-07T20:42:45Z")
Took me a while but can see it now! * * * [cup cake stand](http://cupcakestandstore.co.uk) [Previous page](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555.md?page=1) [Next page](https://boards.straightdope.com/t/what-kind-of-optical-illusion-is-this-pic-in-thread/614555.md?page=3)