# Best optical illusion EVER! **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [July 10, 2006, 7:06am UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834 "2006-07-10T07:06:14Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![js\_africanus](https://avatars.discourse-cdn.com/v4/letter/j/87869e/32.png) [@js\_africanus](https://boards.straightdope.com/u/js_africanus)\ **Post date:** [July 10, 2006, 5:13pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/21 "2006-07-10T17:13:41Z")
[QUOTE=Anaamika] I am constantly amazed at how our eyes trick us. [/QUOTE] Shhhhh. If the eyes find out you know, it’ll be curtains for you! ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [July 10, 2006, 5:36pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/22 "2006-07-10T17:36:44Z")
[QUOTE=Mindfield] The castle though – I can’t really tell if the apparent change is a result of the apparent changes around it giving it the illusion of “real” colour, or if the castle’s complimentary is subtly but importantly differtent enough to give it that “natural” look. [/QUOTE] The negative image is blue, sort of a cerulean shade. The compliment of that is orange, or more like a burnt sienna. Stone in sunlight often appears a subtle shade of this color. Since we tend to filter out this color as a sun effect, it can tend to be very subtle, so the stone may appear to still be gray. I think. Let me check again. Yep. But it’s really subtle. ---
**Author:** ![js\_africanus](https://avatars.discourse-cdn.com/v4/letter/j/87869e/32.png) [@js\_africanus](https://boards.straightdope.com/u/js_africanus)\ **Post date:** [July 10, 2006, 5:38pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/23 "2006-07-10T17:38:27Z")
[QUOTE=tdn] Yep. But it’s really subtle. [/QUOTE] Yeah, I was really impressed how the shades in the blue matched the architecture. Unless my eyes were playing tricks on me. 🙂 ---
**Author:** ![Gangster\_Octopus](https://avatars.discourse-cdn.com/v4/letter/g/a8b319/32.png) [@Gangster\_Octopus](https://boards.straightdope.com/u/Gangster_Octopus)\ **Post date:** [July 10, 2006, 5:40pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/24 "2006-07-10T17:40:26Z")
That’s pretty cool. This has always been the neates optical illusion IMO… [http://web.mit.edu/persci/people/adelson/checkershadow\_illusion.html](http://web.mit.edu/persci/people/adelson/checkershadow_illusion.html) ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [July 10, 2006, 6:13pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/25 "2006-07-10T18:13:07Z")
[QUOTE=Gangster Octopus] This has always been the neates optical illusion IMO… [/QUOTE] Yeah, that’s cool, too. It’s a basic principle of art that a shade is often defined in terms of contrast. That’s a better example than I’ve seen in any art book, though. ---
**Author:** ![Lionne](https://avatars.discourse-cdn.com/v4/letter/l/8e8cbc/32.png) [@Lionne](https://boards.straightdope.com/u/Lionne)\ **Post date:** [July 10, 2006, 6:21pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/26 "2006-07-10T18:21:51Z")
Oo I like that one. Very different. ---
**Author:** ![garygnu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garygnu/32/2924_2.png) [@garygnu](https://boards.straightdope.com/u/garygnu)\ **Post date:** [July 10, 2006, 9:33pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/27 "2006-07-10T21:33:25Z")
You can do it youself with Photoshop: 1) Open a color picture 2) Copy the background into a new layer 3) Invert the colors on the bottom version. The example has more done to it than this, you can blur you own image a lot and it still works. 4) Desaturate the top layer 5) If you need to, make a dot on a new layer 6) With the top, desaturated copy hidden, and the mouse ready to click it back on, stare at the inverted version. 7) After 20 second or so, click the desaturated version back on. Bingo. ---
**Author:** ![Talon\_Karrde](https://avatars.discourse-cdn.com/v4/letter/t/c5a1d2/32.png) [@Talon\_Karrde](https://boards.straightdope.com/u/Talon_Karrde)\ **Post date:** [July 10, 2006, 10:04pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/28 "2006-07-10T22:04:14Z")
I used to sort of know how it worked. Something about the cones in your eyes running out of a particular color, and then compensating by adding something else in. I’m pretty sure I’ve got it wrong here though. ---
**Author:** ![kniz](https://avatars.discourse-cdn.com/v4/letter/k/c37758/32.png) [@kniz](https://boards.straightdope.com/u/kniz)\ **Post date:** [July 10, 2006, 10:13pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/29 "2006-07-10T22:13:26Z")
[QUOTE=Mindfield] it sort of lost its magic. [/QUOTE] 😛 **You are only impressed with _real_ magic, huh?** ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [July 10, 2006, 10:25pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/30 "2006-07-10T22:25:06Z")
Jesus Christ! That bloody ghost woman carrying her screaming head under her arm as she jumped off the parapet scared the piss out me! ---
**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:** [July 10, 2006, 11:01pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/31 "2006-07-10T23:01:21Z")
[QUOTE=Mindfield] The castle though – I can’t really tell if the apparent change is a result of the apparent changes around it giving it the illusion of “real” colour, or if the castle’s complimentary is subtly but importantly differtent enough to give it that “natural” look. [/QUOTE] I just downloaded the image and inverted it in my graphics editor; there is definitely a pale brown colour being imposed on the castle. I think the image was actually constructed like this: [spoiler]Make two copies of the image; desaturate one completely to get a greyscale version; split the other one into CYMK channels, recombine them, discarding the black channel (or replacing it with an empty image of the same size). Invert the recombined image and place a black dot in the same position on both pictures. The monochrome image provides the black channel; colour fatigue inversion provides the CYM. [/spoiler] ---
**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:** [July 10, 2006, 11:12pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/32 "2006-07-10T23:12:22Z")
I’m sure that’s how it’s done, in fact, because when I recombined the image based on the above assumptions, I got [this](http://www.gurman.co.uk/stuff/manzanarecombined.jpg). ---
**Author:** ![levdrakon](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@levdrakon](https://boards.straightdope.com/u/levdrakon)\ **Post date:** [July 10, 2006, 11:24pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/33 "2006-07-10T23:24:50Z")
[QUOTE=Gangster Octopus] That’s pretty cool. This has always been the neates optical illusion IMO… [http://web.mit.edu/persci/people/adelson/checkershadow\_illusion.html](http://web.mit.edu/persci/people/adelson/checkershadow_illusion.html) [/QUOTE] That’s very cool. I couldn’t quite believe it, so I cut & pasted both tiles into separate windows and sure enough, it’s true. Dang. ---
**Author:** ![Moe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/moe/32/2972_2.png) [@Moe](https://boards.straightdope.com/u/Moe)\ **Post date:** [July 10, 2006, 11:24pm UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/34 "2006-07-10T23:24:53Z")
[QUOTE=Talon Karrde] I used to sort of know how it worked. Something about the cones in your eyes running out of a particular color, and then compensating by adding something else in. I’m pretty sure I’ve got it wrong here though. [/QUOTE] Sorta. I believe the effect is due to the opponent processing channels of your visual system. Your sensory neurons (in this case, cones) are always firing at a steady rate. Let’s call that rate 5, on an arbitrary scale of 1 - 10. There are 3 channels for processing color: red/green, blue/yellow, and brightness (or contrast, or something like that. I’m going on memory here). When the cones see red, they fire more quickly, closer to 10. When they see green, they become inhibited, closer to 1. If you stare at red constantly, making them fire, say at about 8, your perceptual system will try to adapt by interpreting 8 as a new baseline. When you remove the red stimulus the cones go back down to 5, but the perceptual system now interprets that as green. BTW, this could be complete bullshit. This is all from what I remember from a course I took about 10 years ago. ---
**Author:** ![MysteryFellow63427](https://avatars.discourse-cdn.com/v4/letter/m/a88e4f/32.png) [@MysteryFellow63427](https://boards.straightdope.com/u/MysteryFellow63427)\ **Post date:** [July 11, 2006, 1:27am UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/35 "2006-07-11T01:27:30Z")
[QUOTE=astro] Jesus Christ! That bloody ghost woman carrying her screaming head under her arm as she jumped off the parapet scared the piss out me! [/QUOTE] I think you were staring at the photo for too long. ---
**Author:** ![Rico](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rico/32/3582_2.png) [@Rico](https://boards.straightdope.com/u/Rico)\ **Post date:** [July 11, 2006, 2:10am UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/36 "2006-07-11T02:10:01Z")
[QUOTE=Mangetout] I’m sure that’s how it’s done, in fact, because when I recombined the image based on the above assumptions, I got [this](http://www.gurman.co.uk/stuff/manzanarecombined.jpg). [/QUOTE] AWESOME! Well done! ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [July 11, 2006, 2:19am UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/37 "2006-07-11T02:19:57Z")
It was a cool effect but it only lasted about a quarter second for me. ---
**Author:** ![Cartooniverse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cartooniverse/32/3084_2.png) [@Cartooniverse](https://boards.straightdope.com/u/Cartooniverse)\ **Post date:** [July 11, 2006, 2:40am UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/38 "2006-07-11T02:40:40Z")
I wonder- I know this is not IMHO but it seems to me that a poll is needed here, because I suspect that our eyes process the images differently ( in a subtle way ) based on the intensity of what is presented. Possible? So, I ask- for anyone who has posted so far, and anyone who checks out that cool link in the OP and wil post in- are you looking at a CRT tube monitor or an LCD monitor, and if it is an LCD monitor, how good is it? I’m viewing an Apple 23 inch Cinema Display monitor- very high res, fairly bright. I hope this doesn’t feel like a hijack, it seems that the type of display may directly correlate to how long people enjoy the effect. I only saw it for a half-second at best, but my god that’s a great effect !! Cartooniverse ---
**Author:** ![Rico](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rico/32/3582_2.png) [@Rico](https://boards.straightdope.com/u/Rico)\ **Post date:** [July 11, 2006, 2:45am UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/39 "2006-07-11T02:45:26Z")
I’m using a 5 year old 15" LCD at 1024x768 and 96dpi. Nothing great, but I see it beautifully. ---
**Author:** ![Mr.Goob](https://avatars.discourse-cdn.com/v4/letter/m/c77e96/32.png) [@Mr.Goob](https://boards.straightdope.com/u/Mr.Goob)\ **Post date:** [July 11, 2006, 3:23am UTC](https://boards.straightdope.com/t/best-optical-illusion-ever/363834/40 "2006-07-11T03:23:14Z")
I’ve a LCD laptop and saw the color for about a second. [Previous page](https://boards.straightdope.com/t/best-optical-illusion-ever/363834.md?page=1) [Next page](https://boards.straightdope.com/t/best-optical-illusion-ever/363834.md?page=3)