Talk:Afterimage

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Afterimage[edit]

Don't want to complain, but that afterimage I get from the "Afterimage"-thing is definitely blue on pink rather than blue on maroon.--91.180.143.27 (talk) 15:35, 6 June 2009 (UTC)

Just noticed, in the bit beneath it, it says "a green image should produce a magenta afterimage" and that's exactly it, so I'm editing maroon into magenta, then.--91.180.143.27 (talk) 15:37, 6 June 2009 (UTC)

Flag Image[edit]

Any pictures besides the United States flag (with appropriate color substitution) to include in the main Afterimage page??

The inverse U.S. flag is a fairly classic example of the afterimage effect; I've seen it elsewhere. Why do you want to change it?

It is unbelievable the subversiveness of having to fix our eyes on the USA flag. Why not another country? If you saw it, it was probably in a US book. The image should be abstract and impartial. It is unacceptable. —Preceding unsigned comment added by 194.80.199.152 (talk) 18:08, 9 January 2008 (UTC)

You want another image, make another image. All you have to do is invert the colours! Leushenko (talk) 03:13, 4 February 2008 (UTC)

Actually upon thinking about it, a more neutral image would be great, but what would it be? The only thing that comes to mind is a selection of flags.... and then we could be upset about precedence instead...Leushenko (talk) 14:51, 6 April 2008 (UTC)
I once saw an afterimage effect that included movement. You stared at a spiral/whirlpool thing for thirty seconds, and then looked at a picture of clouds. The result was that the clouds then started to shimmer like water, due to the afterimage of the spiral overlaid on the clouds. It was a really interesting effect and would only require a simple animated gif. --ErgoSum88 (talk) 15:57, 6 April 2008 (UTC)
Switzerland maybe? (which might also be close to the emblem of the International Red Cross) Jimw338 (talk) 18:57, 16 April 2015 (UTC)

Not rods and cones[edit]

There is not universal agreement about wheither a negative afterimage results from adaption of cones; increasingly people are looking at adaption in ganglion cells in the retina and cells in the lateral geniculate nucleus of the brain.--Heida Maria 14:46, 22 November 2005 (UTC)

But I thought one can rule out LGN neurons' being primarily responsible for afterimages by showing that pressure blinding abolishes afterimages. That would be consistent with afterimages' being mediated by the photoreceptors or by the retinal ganglion cells. Robert P. O'Shea 07:06, 26 April 2007 (UTC)
Pressure blinding eliminates afterimages? Not according to Craik, K. J. W. (1940) Origin of the visual after-image. Nature, 145, 512? He induced an afterimage in participants while pressure blinding them. JohnB90 (talk) 21:12, 23 June 2011 (UTC)
Yes. You are right. There is at least one mysterious thing about that paper. Craik viewed a bright light with both eyes, including the pressure-blinded one; this will ensure that an afterimage is developed though the normal eye, which in my opinion would be difficult to distinguish from that from the pressure-blinded eye. Craik seemed to claim that the afterimage from the normal eye could be abolished by closing it, which is unlikely (closing the eye is one of the usual techniques for seeing an afterimage). Nevertheless, Craik said he was able to see the afterimage from the pressure-blinded eye because it was not at fixation, the pressure blinding having turned that eye away from the light slightly. If we accept Craik's observations, then we are left with his conclusion that the afterimage *is* generated in the photoreceptors, because he says that the pressure blinding allows the photochemical processes in the rods and cones to continue but blocks activity in the retinal ganglion cells.Robert P. O'Shea (talk) 05:34, 30 September 2012 (UTC)

I agree with Heida. There is not a single research paper which confirms the whole "retinal burn in" type of theory which this article suggests. There is only one citation to "support" this in the current article. But when this citation's research publication is actually read, it says nothing about any proof for this theory. It merely mentions it as an afterthought and an as suggestion with no evidence whatsoever. Furthermore, there are several afterimage illusions which confound such a theory. For example, viewing a white area surrounded by a colored background leads to an afterimage the size and shape of the white area but with the color of the background. The background does not necessarily take a complementary afterimage color. There is also strong evidence that afterimages are strongly modulated by attentional processes. One such illusion is called something like "afterimage after the image" and can be found by looking that up on the web. This illusion shows how only partial afterimages tend to appear after being cued by an outline which corresponds to the shape of a certain color (sorry for the poor explanation here; please look at it for yourself to see what I mean). If anything, this seems to show that afterimages do not likely occur in the retina itself, but could rather be the effect of feedback inhibition of the cortex to the thalamus at multiple levels, most notably the LGN and pulvinar portions for visual aftereffects. This could also easily be extended to explain other aftereffects (e.g. paradoxical heat in the somatosensory system, "aftertones" in the hearing system (maybe not many know about this one, though), etc.) --119.83.246.205 (talk) 02:31, 25 June 2009 (UTC)

Whoops. I wasn't signed in. That last entry was mine. --Aphidz (talk) 02:58, 25 June 2009 (UTC)

Here's the (or at lest a page about this - I think): [1] Jimw338 (talk) 19:13, 16 April 2015 (UTC)

YouTube links[edit]

Information icon.svg

This article is one of thousands on Wikipedia that have a link to YouTube in it. Based on the External links policy, most of these should probably be removed. I'm putting this message here, on this talk page, to request the regular editors take a look at the link and make sure it doesn't violate policy. In short: 1. 99% of the time YouTube should not be used as a source. 2. We must not link to material that violates someones copyright. If you are not sure if the link on this article should be removed, feel free to ask me on my talk page and I'll review it personally. Thanks. ---J.S (t|c) 07:29, 7 November 2006 (UTC)

Not just copyright (potentially), but also I assume that all videos on YT eventually get taken down? Otherwise the YT library I assume would grow to.. what - at least an exabyte? I don't remember the stats on how fast YT grows. Then again, Google does seem to be able put an (I presume) unbelievable amount of storage space somewhere (where are Google's server/disk farms - or is that a state secret?)
Spoke too soon - (Some) estimated stats are here, and it works out to about a quarter of a quarter of a petabyte per year (20 TB/month*12*1/1000 TB/PB). Maybe about $12,000 a year, at consumer hard drive prices? Of course, I'm sure Google can get them for less (do they perhaps make their own hard drives?), and they I'm sure they're looking into - or perhaps already using - up-and-coming HDD technologies (SMR, spin-tronic methods, holographic [?]) Jimw338 (talk) 19:32, 16 April 2015 (UTC)

This article needs to be improved[edit]

I'm sorry to be negative, but the level of explanation in this article is simplistic in some places and possibly incorrect in others. Dubious statements include:

  • "This is closely related to the phenomenon called the persistence of vision". If so then persistence of vision would have to involve positive afterimages but the explanation is for negative afterimages. For that matter, positive and negative afterimages are not distinguished.
  • "Normally the eye deals with this problem by rapidly moving the eye small amounts". This does not make sense linguisitically or logically. The eye does not move itself.
  • "the motion later being "filtered out" so it is not noticeable". Citation needed here.
  • "When the eyes are then diverted to a blank space, the tired photoreceptors send out little signal and those colors remain muted." This is very a very confusing sentence.
  • "The green color tires out the green photoreceptors". Although Hering thought there were green photoreceptors, no one thinks that nowadays. There are three cone types that respond to virtually all wavelengths of light but with peak sensitivities for short (S), middle (M), and long (L) wavelengths. A green light will stimulate the M cones the most, the L cones almost as much, and the S cones only a little. The ratios of these activities signal green. After adaptation, the ratios of activities of L, M, and S cones when exposed to white light are supposed to be the same as if the retina had been exposed to light of the complementary colour to the green light.

Perhaps Heida Maria can improve it. She seems to be better up on the literature than I am.Robert P. O'Shea 07:04, 26 April 2007 (UTC)

Images[edit]

The change to Che Guevara as the main image is not exactly any more neutral than the US flag. I propose expanding the gallery with a selection of images, and am wondering if anyone has any ideas for an apolitical image for the article's introduction? The WP logo comes to mind... not sure if that would work. I can't put it to the test on this computer, but will try later. At any rate, more pictures would be good, and none of the current three I think are appropriate for the lead. The flag and portrait are too politically biased and the "Jesus" picture, aside from being totally unencyclopaedic in tone, is also a crappy image (I for one couldn't work it out without looking at the filename). Leushenko (talk) 19:56, 25 July 2008 (UTC)

How is the Jesus picture unencyclopedic? Just because you cant do that one doesnt mean that it doesnt work! I can do it. For 22 more see Here —Preceding unsigned comment added by 88.105.134.147 (talk) 16:23, 8 August 2008 (UTC)
It's unencyclopaedic because it's blatant propaganda and extremely low-quality. It's not a problem to have a religious image, but I object to the subversive portrayal here. Not to mention a standard objection to depictions of Jesus as extremely hirsute, which is irrelevant to the article's content, but factual inaccuracy should not be encouraged. Leushenko (talk) 11:29, 18 August 2008 (UTC)

Are you required to blink?[edit]

Because the only way I can noticeably see most of the afterimages is blinking vigorously after having stared at it for about a minute. 97.118.32.250 (talk) 23:19, 10 May 2010 (UTC)

Intersting artist with afterimage paintings[edit]

Could you create an article about this artist? [2] [3] I do not know how, thank you--Thgiled (talk) 08:39, 2 July 2011 (UTC)

As someone else pointed out on your talk page, there is a article-requesting page. If you feel so passionate about this artist, collect references and learned to edit Wikipedia yourself. Posting the same thing to multiple article talk pages isn't going to help you much. Fred Hsu (talk) 03:25, 3 July 2011 (UTC)

The Color dove illusion redirect[edit]

Apparently there used to be something here about a "Color dove illusion" because there's a redirect by that name that is still used on a figure in the Opponent process article. Anyone know what became of that? Probably the figure in that article should be changed and the redirect removed, but I figured I'd ask first. 71.197.166.72 (talk) 07:44, 3 June 2015 (UTC)

Resolved I've just stumbled upon the same problem and solved it by restoring the illustration, which had been carelessly removed. This had also turned the remaining reference to a bird into a headscratcher. --Florian Blaschke (talk) 18:04, 15 June 2015 (UTC)
A personal comment: I believe I have understood how the color dove illusion works now. When I tried it here, I noticed that when I choose, for example, a green background, not only the white dove appears to have acquired a greenish tint as soon as the background switches to white, but also the white background of the page surrounding the Flash box. What really happens, however, is that the white surrounding the bird acquires a reddish tint as an effect of color vision fatigue, i. e., an afterimage from the green. In contrast with this reddish tint, the white of the bird and the background surrounding the Flash box, which did not change, appears to have a greenish tint as the visual system defaults to the white area surrounding the bird (which has just switched from green to white) as the "true" white. Why the visual system insists that this "new" white is the "true" white is not completely clear to me (I'm reminded of the infamous blue-black/white-gold dress, where the choice of the "true" white and black through the visual system, which turns out to be individually different in this case, determines colour perception), but the reason is probably that the "new" colour is more perceptually salient (like changes and motion in the visual field in general) than the unchanging white of the bird and the background of the page. --Florian Blaschke (talk) 18:32, 15 June 2015 (UTC)