# Color optical illusions. My perception of the world is shaken. **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [July 31, 2005, 1:30am UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954 "2005-07-31T01:30:41Z")\ **Posts on this page:** 19\ **Page:** 4
**Author:** ![Larry\_Mudd](https://avatars.discourse-cdn.com/v4/letter/l/f14d63/32.png) [@Larry\_Mudd](https://boards.straightdope.com/u/Larry_Mudd)\ **Post date:** [August 7, 2005, 3:30am UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/61 "2005-08-07T03:30:29Z")
> [@RickJay](#): > > They are not identical and have a different mix of pixel colors. There is a bit of bleeding due to compression artifacts, but it’s insignificant because the objective colours that do creep in are inverts of the induced colour. To show you that it works beyond a doubt, though, I’ve altered the image a bit and saved it as a .gif, so the colours won’t “run” at all. [Check it out](http://www.larrymudd.com/images/orig_illusion.gif). Every single pixel on both crosspieces is a shade of grey. They are both 50% grey at the “base,” and equally shaded. They are both represented by the [exact same pixels](http://www.larrymudd.com/images/crosspieces.gif), just rotated. Does the illusion still work? 🙂 ---
**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\ **Post date:** [August 7, 2005, 3:55am UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/62 "2005-08-07T03:55:16Z")
Now I am really confused. Your new image looks absolutely nothing like the images in the original picture. I’m comparing them side by side and the originals, cropped and taken away from the rest of the picture, are filled with color. Your FIRST image is significantly changed, in fact. I took the original picture from the Web site, blew up the crosspeices, cut everything else out, and they absolutely are not made up of all grey pixels. Perhaps there is something I am missing technically, but if you blow up the original Web site image, is is plainly obvious that the pixels are not all grey. MOST of them are not grey. If this is the result of “image bleeding” the fact remains that in the original illusion, in terms of what actually is sending light to the observer’s eyes, the image is not all grey; most of the pixels are various shades of pale yellow. Even in your first attempt at isolation, “broken\_illusion,” which is not a very good representation of how the original appears, I can see green, blue, red… The images simply aren’t identical except in your all-grey version. Maybe the original has some artifact of computer graphics causing color to bleed into the grey, but there is color there. ---
**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\ **Post date:** [August 7, 2005, 3:56am UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/63 "2005-08-07T03:56:46Z")
Incidentally, of course the illusion DOES still work, albiet not quite as convincingly, after you changed the pixels to gray (or made them gray by changing it into a gif, whatever.) I liked your illusion better, though. ---
**Author:** ![Larry\_Mudd](https://avatars.discourse-cdn.com/v4/letter/l/f14d63/32.png) [@Larry\_Mudd](https://boards.straightdope.com/u/Larry_Mudd)\ **Post date:** [August 7, 2005, 7:38am UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/64 "2005-08-07T07:38:27Z")
> [@RickJay](#): > > Perhaps there is something I am missing technically, but if you blow up the original Web site image, is is plainly obvious that the pixels are not all grey. You might be surprised to see how little they vary from grey, objectively. If you use the [colorpicker](http://www.larrymudd.com/images/color_picker.gif), you can explore all the pixels in the crosspieces and see what colours they actually are. They are never visibly yellow when taken out of context. When they do visibly vary from grey, they take on the colour from the surrounding pixels, making a sort of purple. [This is the colour of the yellowest pixel from the right crossbar](http://www.larrymudd.com/images/yellowgrey.gif). These pixels are about 1/25th less "blue’ than a perfect grey. Too me, out of context, it looks grey. Does it register as yellow for you? (I wonder how much different people’s thresholds for registering red, blue, or yellow varies?) > [@RickJay](#): > > I liked your illusion better, though. Thankee. ---
**Author:** ![Dark\_Side\_of\_the\_Floyd](https://avatars.discourse-cdn.com/v4/letter/d/bb73d2/32.png) [@Dark\_Side\_of\_the\_Floyd](https://boards.straightdope.com/u/Dark_Side_of_the_Floyd)\ **Post date:** [August 7, 2005, 9:08am UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/65 "2005-08-07T09:08:51Z")
> [@Archergal](#): > > Hey, this isn’t _exactly_ the same thing, but her’s a guy who does pavement art which, when seen from the correct angle, looks 3-dimensional. Very cool > > [Virtual Street Reality](http://www.rense.com/general67/street.htm) Astounding. ---
**Author:** ![Larry\_Mudd](https://avatars.discourse-cdn.com/v4/letter/l/f14d63/32.png) [@Larry\_Mudd](https://boards.straightdope.com/u/Larry_Mudd)\ **Post date:** [August 8, 2005, 8:38pm UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/66 "2005-08-08T20:38:43Z")
Hey, this is weird. Something I stumbled across while trying to sort out some linguistic Tolkieana might lend some insight into the phenomenon exploited in the induced colour illusions. The words we have for “blue” and “yellow” are [connected](http://www.etymonline.com/index.php?term=blue), if you go back as far as the Proto-Indo-European roots, when the same word was used for both hues. This peculiarity continued for a long time, too. In Old English, it became _“blaw”_, (“blue.”) In Old Spanish, it became _“blavo”_, (“yellowish grey.”) In Welsh, _blawr_, “grey.” > [@](#): > > **blue** > c.1300, _bleu, blwe, etc._, from [O.Fr](http://O.Fr). _bleu_, from Frank. blao, from P.Gmc. \*_blæwaz_, from PIE base \*_bhle-was_ “light-colored, blue, blond, yellow.” "The exact color to which the Gmc. term applies varies in the older dialects; M.H.G. _bla_ is also “yellow,” whereas the Scandinavian words may refer esp. to a deep, swarthy black, e.g. O.N. _blamaðr_, N.Icel. _blamaður_ ‘Negro’ " [Buck]. Replaced O.E. _blaw_, from the same PIE root, which also yielded L. _flavus_ “yellow,” O.Sp. _blavo_ “yellowish-gray,” Gk. _phalos_ “white,” Welsh _blawr_ “gray,” O.N. _bla_ “livid” It’s possible the opposition of yellow and blue that we see is something that human beings did not _always_ see. [Neuroscientists can’t reconcile our biology with a 4-hue oppositional model](http://www.bbsonline.org/Preprints/OldArchive/bbs.saunders.html), and the whole “yellow vs. blue” thing is particular sticking point: > [@](#): > > If we look at the possibility of a blue/yellow neural pathway the situation is still more confused. As many as nine different ways have been reported for cones and rods to be connected to retinal ganglion cells (Gouras 1984). L/M cells predominate, but a small number of ganglion cells are definitely connected to S cones. They have been called blue/yellow opponent cells, but this means no more than that they are connected to S cones as well as to the L and/or M cones. They respond positively to blue/violet light, but it is not clear how they respond to a yellow signal (Gouras 1984, Zrenner 1983). > > The suggestion that there is no neurophysiological evidence for the existence of exactly two pairs of opponent hues is not new. Gouras and Eggers (1984) deny Hering’s opponent colour channels in the primate retinogeniculate pathway. D’Zmura (1991, p. 951) says “observers [also] possess chromatic detection mechanisms tuned to intermediate hues such as orange.” Teller (1991, p. 530) suggests: “[t]he retinal coding scheme requires further recoding if neurons fully worthy of the name red/green and (particularly) yellow/blue are to emerge. Such neurons have not yet been seen in primate visual systems, and no one knows where or whether they will ever be seen.” Similarly Mollon (1992) reviewing Davidoff (1991), claims the latter’s appeal to “chromatically opponent neurons that signal redness and greenness or blueness and yellowness” is pseudo-physiology because “the neurons he requires to substantiate his view are not those that have so far been found electrophysiologically in the visual pathway.” Okay, _now_ my perception of the world is shaken. [chuck heston] The colour blue is _yellow!__YELLOOW!_ [/chuck heston] ---
**Author:** ![Velma](https://avatars.discourse-cdn.com/v4/letter/v/85e7bf/32.png) [@Velma](https://boards.straightdope.com/u/Velma)\ **Post date:** [August 8, 2005, 9:15pm UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/67 "2005-08-08T21:15:04Z")
I find that after going back to the 3rd illusion (which worked for me as intended the first time) I could train myself to see them as grey all the time. I moved the mask over as shown to make my eyes see them both as grey. Then I moved it a little around the blue side cross so that I could see the grey by itself first, then with a little blue next to it. I circled the mask opening around the cross to let myself see the grey with the blue. When I removed the mask, I saw both crosses as the same color grey, even when I briefly looked away and looked back. When I looked away for a few seconds and looked back again, then I saw them as grey and yellow again. Try it - you’ll feel better that you can really see the colors if you try! 🙂 ---
**Author:** ![Larry\_Mudd](https://avatars.discourse-cdn.com/v4/letter/l/f14d63/32.png) [@Larry\_Mudd](https://boards.straightdope.com/u/Larry_Mudd)\ **Post date:** [August 10, 2005, 7:42am UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/68 "2005-08-10T07:42:16Z")
I was arsing around with recursive actions in Photoshop today to make a version of one of my favourite optical illusions: [Retinal motion](http://www.larrymudd.com/images/motion_illusion.gif). (AKA “Trippy snakes.”) 😃 ---
**Author:** ![sturmhauke](https://avatars.discourse-cdn.com/v4/letter/s/e47c2d/32.png) [@sturmhauke](https://boards.straightdope.com/u/sturmhauke)\ **Post date:** [August 10, 2005, 8:01am UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/69 "2005-08-10T08:01:27Z")
Dude, I never dropped acid but that’s almost enough to trigger a flashback anyway. Like, whoa. ---
**Author:** ![sturmhauke](https://avatars.discourse-cdn.com/v4/letter/s/e47c2d/32.png) [@sturmhauke](https://boards.straightdope.com/u/sturmhauke)\ **Post date:** [August 10, 2005, 8:52am UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/70 "2005-08-10T08:52:22Z")
I found a very trippy illusion on [this page](http://www.skytopia.com/project/illusion/illusion.html), which incidentally has Larry’s favorite and the OP’s #1. The one I have in mind is near the bottom, and it’s called Vision Distorter. You watch one of 4 animations of diagonal black and white stripes moving in different ways, then you look at any other object and it appears to warp and change. I find the illusion is strongest with a color photo or painting, but you can also look at your hand and freak out when demons start writhing around under your skin. [sub]OK, not really, but it looks really weird.[/sub] ---
**Author:** ![Sal\_Ammoniac](https://avatars.discourse-cdn.com/v4/letter/s/8dc957/32.png) [@Sal\_Ammoniac](https://boards.straightdope.com/u/Sal_Ammoniac)\ **Post date:** [August 10, 2005, 1:09pm UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/71 "2005-08-10T13:09:09Z")
If there’s a lesson here – and there has to be a lesson, right? – it’s to be careful when choosing paint for your walls. The paint you love at the paint store might look completely different at home, for a variety of reasons involving context, not to mention lighting. (I’ve noticed that different kinds of light bulbs make colors look radically different. Those energy-efficient bulbs give everything a weird greenish tinge, but incandescents makes a lot of colors better.) Plus I want to give a shout-out to **Larry Mudd** for going the extra mile. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 10, 2005, 1:16pm UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/72 "2005-08-10T13:16:22Z")
This thread is kind of amusing, because… stay with me here… there’s this illusion where one grey object looks blue and another one looks yellow, even though they are actually the same colour, or as near as dammit, but the funny part is that (unless I’m just misunderstanding what they’re saying) we’ve got people saying it doesn’t work because one looks blue and the other looks yellow. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [August 10, 2005, 1:52pm UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/73 "2005-08-10T13:52:50Z")
To all those who “can’t see” the # 3 illusion, are you using he pull down mask at the top? It’s pretty necessary to get the effect. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [August 10, 2005, 2:20pm UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/74 "2005-08-10T14:20:42Z")
I have to admit that #3 doesn’t work for me at all – it doesn’t look yellow on the right. And I’m not color blind. #1 and #2 are pretty startling, though. ---
**Author:** ![nivlac](https://avatars.discourse-cdn.com/v4/letter/n/3bc359/32.png) [@nivlac](https://boards.straightdope.com/u/nivlac)\ **Post date:** [August 11, 2005, 7:41am UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/75 "2005-08-11T07:41:38Z")
> [@Mangetout](#): > > This thread is kind of amusing, because… stay with me here… there’s this illusion where one grey object looks blue and another one looks yellow, even though they are actually the same colour, or as near as dammit, but the funny part is that (unless I’m just misunderstanding what they’re saying) we’ve got people saying it doesn’t work because one looks blue and the other looks yellow. No, what we are saying is that we don’t see the supposed effect. Both cross-pieces look grey, although the one on the left is a slightly darker shade of grey. > [@astro](#): > > To all those who “can’t see” the # 3 illusion, are you using he pull down mask at the top? It’s pretty necessary to get the effect. Huh? Isn’t the idea to see the illusion without the mask. The mask is used to cover all the irrelevant parts that make the illusion work, i.e., the mask will take away the illusion. In my case, with or without the mask, no illusion for #3. ---
**Author:** ![sturmhauke](https://avatars.discourse-cdn.com/v4/letter/s/e47c2d/32.png) [@sturmhauke](https://boards.straightdope.com/u/sturmhauke)\ **Post date:** [August 11, 2005, 9:52am UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/76 "2005-08-11T09:52:22Z")
Some people are more susceptible to illusions for some reason. **available light** for example seems to take longer to observe their effects compared to me, and they seem to be less striking for her. ---
**Author:** ![stnic](https://avatars.discourse-cdn.com/v4/letter/s/8c91f0/32.png) [@stnic](https://boards.straightdope.com/u/stnic)\ **Post date:** [August 11, 2005, 3:16pm UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/77 "2005-08-11T15:16:36Z")
I assume that none of you had basic color theory in high school art class. Joseph Albers, who taught at the Bauhaus, wrote a really great book with fantastic examples on how color is affected by other color. These are things taught (or should be) in basic design classes and some students do some incredible work while learning these basic concepts. ---
**Author:** ![Kythereia](https://avatars.discourse-cdn.com/v4/letter/k/e8c25b/32.png) [@Kythereia](https://boards.straightdope.com/u/Kythereia)\ **Post date:** [August 11, 2005, 3:34pm UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/78 "2005-08-11T15:34:22Z")
[Keanu] Whoa. [/Keanu] ---
**Author:** ![sturmhauke](https://avatars.discourse-cdn.com/v4/letter/s/e47c2d/32.png) [@sturmhauke](https://boards.straightdope.com/u/sturmhauke)\ **Post date:** [August 11, 2005, 7:42pm UTC](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954/79 "2005-08-11T19:42:16Z")
> [@stnic](#): > > I assume that none of you had basic color theory in high school art class. You assume wrongly. These illusions go beyond what I would normally expect to see. [Previous page](https://boards.straightdope.com/t/color-optical-illusions-my-perception-of-the-world-is-shaken/314954.md?page=3)