Talk:Checker shadow illusion

message: This article definitely needs a different picture, in the one showing at the moment square A is obviously darker than square B.  —Preceding unsigned comment added by 129.240.146.29 (talk) 13:28, 7 December 2009 (UTC)
replies: text: Sigh. -- 98.108.219.226 (talk) 05:49, 24 February 2010 (UTC)
replies: text:  Yes, it is in fact darker if the image is interpreted as a 3D projection. But the optical illusion is that it still looks darker on the 2D plane of the projection (i.e. pixels of the image file), which we cannot truly conceive as a whole, because we cannot entirely disable our spatial perception which automatically makes the shadowed area of lighter color because it does correct for 3D lighting. I added the projection logic to the article's explanation of the optical illusion.37.201.227.22 (talk) 07:52, 17 July 2014 (UTC)
thread_title: Wrong picture

message: https://en.wikipedia.org/wiki/File:Optical_illusion_greysquares.gif
Sean McHugh (talk) 08:19, 5 March 2014 (UTC)
replies: text: In my opinion too this animation is the only convincing demonstration that these two squares are really the same color. Without this animation, I couldn't convince myself they are. Nyh (talk) 09:08, 21 January 2020 (UTC)
thread_title: Who removed the useful illusion deconstructed?

message: I think this page should be titled Same color illusion. NickelShoe 14:57, 16 December 2005 (UTC)
thread_title: Move?

message: If I squint, and cover the green cylinder with my hand, I can see the identity! Try it! DS 14:55, 21 January 2006 (UTC)
replies: text: It works to me. I don't have to squint deliberately as I have a slight squint anyway, but if I put my finger between squares A and B they appear the same colour to me. Wouldnt that be the best way to invite people to test it?130.88.123.189 (talk) 12:04, 20 April 2009 (UTC)

text: Sigh. It's not a mock-up, they are the same color. -- 98.108.219.226 (talk) 05:54, 24 February 2010 (UTC)
thread_title:  Yay! 

message: There used to be links to Flash files and other animations that show the truth of the same-colorness much better than the animated gif does. Where did those links go??? 70.20.147.17 12:33, 7 August 2006 (UTC)
thread_title:  Missing Links 

message: It seems like most other optical illusions stubs are classified as psychology stubs.  Is there any particular reason why this one is called an optics stub instead? Stebbins 06:59, 8 November 2006 (UTC)
thread_title:  Physics or Psychology? 

message: Wouldn't joining squares A and B with line of the same color (in the green cylinder image) make the simmilarity more obvious ? I mean  something like this---- Xil/talk 17:01, 7 May 2007 (UTC)
replies: text: Yes, i agree, your image does make the similarity more obvious Rombust 09:20, 14 June 2007 (UTC)
replies: text: Not entirely - To me it looks like the current bridge of the "same color" is actually a gradient of shades, lighter on one end than on the other. (Certainly I believe you that the bridge is just one color - There just isn't that "aha!" moment where I can see for myself it is.) -- 128.104.112.147 (talk) 14:36, 2 June 2008 (UTC)
replies: text: (Should have clicked on Xil's link instead of assuming it was the same as the current image ()) To me, the wider band of Xil's image does a better job than the narrow one currently used. -- 128.104.112.147 (talk) 14:41, 2 June 2008 (UTC)
thread_title: Visible simmilarity

message: When the article says the squares are the same color,
it is making the same mistake it is trying to educate
readers about.
It is only the physical parallelogram-shaped regions
in the image that are the same color.  There are no
actual squares in the image.
The squares are in the perceived scene.  Since the image
has shading representing a cylinder and its shadow,
you can't say that the squares are not the same color.  —Preceding unsigned comment added by 216.1.16.126 (talk) 23:18, 3 February 2009 (UTC)
replies: text: That's pointlessly pedantic -- and incorrect. This article is not about 2D representations of 3D objects. -- 98.108.219.226 (talk) 05:58, 24 February 2010 (UTC)
thread_title:  Conflating Squares vs. Representations of Squares 

message: It seems to me that this article is missing something rather important. Does anyone know if this illusion has been explained and, if so, what the explanation is? This is what I came here to find.  —Preceding unsigned comment added by 86.142.90.162 (talk) 12:19, 4 October 2009 (UTC)
thread_title:  Explanation? 

message: Imagine that instead of having a computer image or drawing of a checkerboard and a cylinder shadowing it, we had an actual checkerboard, cylinder and lamp.  In the real checkerboard, we have the corresponding squares labeled A and B.  We carefully set up the light intensity, checkerboard square tint and viewer position so that A and B reflect the same total amount of light back to the viewer.
Would you say that the viewer who judged that A is darker than B in this situation is falling for an optical illusion?  Heck no.  That viewer is correctly judging the color of the squares, understood as their surface reflectivity.  Our vision is very good at judging the surface reflectivity under mixed light; if we simultaneously see a black cat in the sunshine and a white cat in the deep shadow under a car, we correctly judge which cat's hair is darker, despite the fact that the eye probably in fact receives more light from the black cat than from the white one.
But the naïve idea that there is a "same color illusion" in the checkboard-and-cylinder image would require us to conclude that the guy who sees the black cat in the sunshine and the white can in the shadow is experiencing an illusion.  The black cat would be "objectively brighter" because it's in the sunshine, and thus, reflecting more light than the white one!
Or in other terms: the argument that A and B are "the same color" has this structure:
* The light from points A and B (A ≠ B) that reaches our retina at points A' and B' (A' ≠ B') has the same intensity and spectral composition.
* Ergo, A and B have the same color.
But again, it's trivial to construct examples where the premise is true and the conclusion is wrong.  Even worse with the black and white cat example—you can construct examples where the darker point is the one with more light!
There are optical illusions in the image, but they're really just the illusions of depth and light.  The image is seen as a depiction of a physical scene where square A is darker than B—i.e., where square A reflects a smaller percentage of the light that falls on it than B.  In fact, you have to judge A as being darker than B to correctly see this image as a depiction of a scene, and not just a bunch of colored patches—just as you have to judge those irregular parallelograms as squares to perceive the perspective rendering as a checkerboard.  63.80.102.10 (talk) 23:50, 11 April 2011 (UTC)
replies: text: One thing you might consider doing is posting a question like this on the Science reference desk. Bus stop (talk) 02:04, 12 April 2011 (UTC)
replies: text: I do not see where the OP is asking a question. 86.148.155.92 (talk) 11:33, 26 June 2012 (UTC)
thread_title:  Another shot at this 

message: I looked at the history, and sources, and couldn't find any sources calling it the "same color illusion" or "Adelson's checker shadow illusion" from before this article called it those things.  Just "checker shadow illusion", or in a few cases preceded by the indentification as "Ted Adelson's" or "Edward Adelson's"; never just "Adelson's".  So I simplified it and moved it what it's always called in sources, neglecting those recent ones that copied from wikipedia.  Dicklyon (talk) 22:32, 17 April 2011 (UTC)
thread_title:  Moved and cleaned up names 

message: I've come to this rather late I know, but I see there is still some activity here. It seems to me that the Explanation of the effect is OK, but I'll have another go.
If you can, ignore the shadow effect. Look at the image as two squares: A is surrounded by light grey and B is surrounded by very dark grey to black. The shadow effect merely makes the surroundings of B even darker.
It is known that, a shade surrounded by much lighter shades looks darker, while the same shade, surrounded by darker shades looks lighter. Sadly, the illusion I remember from 1st year Psychology a million years ago doesn't seem to be in WP - I'll look for it. However, a similar effect is shown by the picture in the article showing the two coloured circles on the checkerboard, and the colour-gradient effect.
I've tried this in MS Paint, just using two grey squares, one surrounded with white, and the other surrounded by black. The two squares do look like different shades, but they are not. I did the same with two yellow circles too - same effect. Myrvin (talk) 13:58, 14 July 2014 (UTC)
thread_title:  Possible explanation and example 

message: This article is really funny. Obviously, the two squares have different colors. Anyone can see that. Giving this article the benefit of the doubt, I cut two little holes in a piece of paper, and took a look. Sure enough. Different colors! What a joke. There are famous psychology experiments that show how sheepishly people believe any kind of old nonsense, as long as it has the stamp of authority and other "subjects" (actually part of the experiment) believe it. Obviously, this article is not an experiment. It's a result of the incredibly flawed Wikipedia process. But the result is the same. I find it amusing how people believe anything they read or see on Wikipedia. If Wikipedia said 2 + 2 = 5, people would believe it. There is a sucker born every minute, and apparently gets their information from Wikipedia. If some wanted to make a satire web site of Wikipedia, they couldn't do any better than the original. Don't get me wrong. If I want to get the details on an episode of Buffy the Vampire Slayer, Wikipedia is my first choice. Wikipedia has a wealth of information on everything that does not matter. But for anything of a scientific or technical nature, Wikipedia is not a reliable source. This article is just one particularly striking example. 71.217.116.182 (talk) 23:33, 14 July 2014 (UTC)
replies: text: Instead of just being critical, why not add some information you feel is missing?  Wikipedia is only as good as the people who edit it. Not everyone is a scientist or engineer.  As this comment has little to do with this article, I would suggest any further statements of dissatisfaction with Wikipedia be placed elsewhere. 331dot (talk) 23:34, 14 July 2014 (UTC)
thread_title:  The emperor has no clothes 

message: Hello. Is there any reason to believe that the "Explanation" section is not a copyright violation and that the "Variations of the illusion" section is not original research? Thanks and regards, Biwom (talk) 07:02, 16 November 2017 (UTC)
replies: text: So, after a 24-hour delay, I have removed both sections. Thanks and regards, Biwom (talk) 08:14, 17 November 2017 (UTC)
replies: text: I have rolled back your edits. I don't think the section quoting the author of the illusion is a CV - it makes the correct attribution. And as for OR, that calls for some discussion. Eusebeus (talk) 10:24, 19 November 2017 (UTC)
replies: text: Hello. I think our policies about copyvio and unsourced content are clear. If you want this in the article, you need to reword the "Explanations" and find sources for the "Variations". Thanks and regards, Biwom (talk) 10:41, 19 November 2017 (UTC)

text: And in an attempt to kill any discussion before it has even started, let me add this. The reason I strongly believe "Variations" is OR is because it actually contradicts what Adelson says in the copyvio quote. So on one hand, you have Adelson who, with I believe some legitimacy, tells you the illusion works because the cylinder is visible and your brain interprets the darker central zone as its shadow. And on the other hand, you have a new contributor with zero edit and zero source who tells you "most of the board and even the cylinder are actually redundant". Really? Well sorry, but no. So let me add WP:UNDUE and WP:FRINGE to WP:OR and WP:PROVEIT. Thanks and regards, Biwom (talk) 16:47, 19 November 2017 (UTC)
thread_title:  More optical illusions? 

message: I am unsure if at some point when the images got converted to SVG the examples didn't get converted right, or are displaying wrong. When I use a color picker on the :File:Checker_shadow_illusion.svg the color of the A square is #6F6F6F while the color of the B square is #818181. On :File:Grey_square_optical_illusion_proof2.svg both squares are #787877, and the illusion works when I remove the connecting bridge. I am unsure now if this is some quirk of how my browser (Chrome) and editing program (Affinity Designer) render the shadow or a mistake in the first example. I double-checked and what I'm picking is the displayed color after all SVG layers were mixed together.
WhiteRailgun (talk) 19:58, 4 September 2019 (UTC)
replies: text: both thumbnail images were identical except for the added rectangle. Ever since the replacement of :File:Grey_square_optical_illusion.svg with :File:Checker_shadow_illusion.svg, the upper thumbnail is now a bit larger and darker than the lower. Unknown what that accomplished other than complicating any direct comparison. My color picker shows #5C5C5C for both A and B squares in the current upper image, and #656564 for both A and B squares in the lower. I was unable to reproduce your A vs B difference. Rairden (talk) 22:10, 8 July 2020 (UTC)
thread_title:  Possible mistake after SVG conversion