Talk:Emission theory (vision)

50 percent
"50 percent of American college students"? I know we're not the smartest lot, but I think most of us understand that our eyes do not illuminate the objects we look at. This whole article seems a bit fishy, but I don't know enough to edit. Anyone up to it? Xyzzyva 15:56, May 18, 2005 (UTC)


 * I couldn't find any reference for this assertion other than sites that mirror Wikipedia. Anyone else have any information on it? Edwardian 22:25, 25 September 2005 (UTC)


 * I found something that appears to me to cast some suspicion on those findings, but I'm afraid it's beyond my area of expertise to figure it out. Edwardian 06:33, 4 December 2005 (UTC)

I'm going to have a go. There's already another page that refers to Newtonian emission theory, but calls it "emitter theory" - this phrasing is pretty obscure, it only throws up about 300 hits on Google as opposed to about 7,500 for the more usual spelling. And it refers to it as a wave theory based on Maxwell's equations that only became disprovable in the 1960s' (as opposed to the 1910's).

so I think I'll have to rewrite the emitter page (or turn it into a redirect for "emission theory"), and then extend the existing "emission theory" page. Maybe rename the "eye-ray" stuff (which doesn't seem to provide any supporting links or references) to emission theory (vision) or similar, and crosslink. It might even be worth starting a list page of "emission theories" (Newton and Ritz for starters). ErkDemon 8 July 2005 22:38 (UTC)

The 50% actually refers to adults in general, per the source, a more believable statistic. David815 (talk) 18:40, 10 October 2015 (UTC)

Original argument?

 * To convince such students of the error of assuming that light needs to be emitted from an optical device (such as the eye) to accomplish perception, once could say that it would be impossible for a camera to capture an image because the lens of a camera does not emit any light.

This isn't an obvious contradiction; it's perfectly consistent to assume that any image-forming object would emit rays, or that all objects emit rays and a camera simply records its perceptions of nearby objects. I removed the argument. -- Beland 16:19, 25 September 2007 (UTC)

Mind-bogglingly stupid
Errrm... I just know there's going to be a good answer to this, but if we were to see by light emitted from our eyes, why can't we see just as well in the dark? William M. Connolley (talk) 22:57, 30 January 2008 (UTC)
 * According to Plato (Timaeus 45b–e) the light in our eyes is too weak to penetrate the darkness on its own and needs external light. In this respect the extramission theory always presupposes the external light. → Aethralis 09:36, 21 April 2008 (UTC)

Evidence for the theory
The article is very dismissive about there being any evidence for perception by emission. However, Tapetum lucidum describes some examples. --Una Smith (talk) 23:55, 31 May 2009 (UTC)

The article is dismissive because that evidence is demonstrably false and unscientific. The section goes over the basic arguments against this evidence to illustrate their fallacy. I am removing the neutrality tag unless there is something I am misssing. -- Jieagles (talk) 07:44, 16 August 2009 (UTC) I am surprised that "emission theory" is still as long as it is, because it is nonsense. Una is wrong to claim that the tapetum lucidum of some eyes is an example of emission - it is an example not of emission, but of reflection (from the tatetum lucidum itself, behind the retina of many nocturnal vertebrates. DJMcC (talk) 11:08, 12 April 2012 (UTC)

That's all from modern physics?
"Modern physics has confirmed that light is physically transmitted by photons, from a light source such as the sun, to visible objects, and finishing with the detector, such as a human eye or camera."

Shouldn't there be more here about modern physics and the wave function requirement for an observation? Physics has shown that the act of observation does something similar to putting out a wave of its own that mingles with the light wave to create a particle. Patsobest (talk) 07:41, 22 June 2012 (UTC)

What modern physics tells us, Patsobest, is that light sensing in the eye is a result of the biochemical transduction pathway initiated by the absorption of a photon by an opsin-retinal complex in a photoreceptor cell. No particle creation necessary, only a change of state of the biomolecule, triggering a reaction cascade in the cell. See: http://en.wikipedia.org/wiki/Visual_phototransduction for more detail. DJMcC (talk) 16:01, 27 July 2012 (UTC)
 * That's what classical physics tells us. Modern physics, or a certain interpretation thereof, tells us that an observation of a quantum state "causes" wave-function collapse. Maybe that's what Patsobest was obliquely referring to. Of course it's not fiery rays shining out of our eyes, but it calls the idea of observation being completely passive into question.--2.247.246.42 (talk) 09:55, 21 July 2019 (UTC)

questionable source
The paragraph
 * Many common phrases in English, such as "bright eyes", "fiery eyes", or "twinkling of an eye" are consistent with the extramission theory of vision.

is based on which violates WP:RS. I'm removing it in addition to the irrelevant content on ray tracing I've already removed. 69.254.215.168 (talk) 21:16, 1 June 2015 (UTC)

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Illustration
The illustration is not from the cited book, but from: update: it is the same book, but it does not have a german title. — Preceding unsigned comment added by Ivoihrke (talk • contribs) 18:30, 20 January 2022 (UTC)

R.P.F. Joannis Zahn... Pro practice construendo et elaborando oculo artificialis teledioptrico (1685) https://archive.org/details/gri_c00133125008631372

page 242 in the pdf.

Also, while it is very suggestive, the upper figure does *not* illustrate emission theory. I have translated the captions and the paragraph on the following page that discuss the upper picture. It is clear that intromission theory is behind the understanding of the author.

Initial chapter question

Quanam causa sive ratio physica esse potest structura ocularis ac fingularum ejus partium ? By what cause or reason can there be a physical structure of the eye and its several parts?

Figure captions ---

sic quasi membranae volitant similaera per auras quaque palet quocunque licet caniunda feruntur So like particles of fine flour flowing through the air

usque a deo omnibus a rebus res quoque fluenter fertur et in cunctas dimittitur undique partes lucretius all the way from God to all things, the thing is also flowing along, and it is released into all parts from all sides.

explanation of upper figure leading up to discussion of points ABC --

Eodem ergo modo omnia puncta specierum ab objecto productarum radios non tam in quaelibet superficiei ocularis, quam singulorum humorum puncta transfundere possunt, qui tamen ope refractionis in ipsis factae ad Retinam colligentur, ibique objecti imaginem perfecte experiment.

In the same way, therefore, all the points of the species produced from the object are rays not so much on any surface of the eye They can transfuse points of the individual fluids, which, however, through the aid of a refraction formed in them, will be collected into the retina, and there is a perfect image of the object in the experiment.

Sic objectum A B C ex singulis suis punctis, quorum tantum tria in figura sunt consignata;, velut A B C radiat & species dimittit quaquaversus in orbem: qui autem radii occurrunt oculo D E F H I G accumprimis humori crystallino D E F eundem transeunt, ut illi radii: qui ab eodem puncto objecti profluunt, ope refractionis per eundera humorem factae in certis Retinae: locis colligantur & uniantur.

Thus the object A, B, C is one of its own the points of which only three are formed in the figure; as A B C radiates and the species it releases in all directions in the circle. But those rays that occur to the eye D E F H I G especially the crystal liquid D E F pass through the same as those rays which flow from the same point of the object, by means of a refraction formed by the earth's moisture they may be collected and united in specific parts of the retina. — Preceding unsigned comment added by Ivoihrke (talk • contribs) 18:26, 20 January 2022 (UTC)

Possibly rooted in how our brain models the gaze of others
There is some research suggesting this, here are a few references taken from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7884070/:


 * Guterstam A, Kean HH, Webb TW, Kean FS, Graziano MSA. Implicit model of other people's visual attention as an invisible, force-carrying beam projecting from the eyes. PNAS. 2019;116:328–333. doi: 10.1073/pnas.1816581115. PMC free article PubMedCrossRef Google Scholar
 * Guterstam A, Wilterson AI, Wachtell D, Graziano MSA. Other people's gaze encoded as implied motion in the human brain. PNAS. 2020;117:13162–13167. doi: 10.1073/pnas.2003110117. PMC free article PubMedCrossRef Google Scholar
 * Guterstam A, Graziano MSA. Visual motion assists in social cognition. PNAS. 2020a;117:32165–32168. doi: 10.1073/pnas.2021325117. PMC free article PubMedCrossRef Google Scholar
 * Guterstam A, Graziano MSA. Implied motion as a possible mechanism for encoding other people's attention. Progress in Neurobiology. 2020b;190:101797. doi: 10.1016/j.pneurobio.2020.101797. PubMedCrossRef Google Scholar

I also ran across some authors arguing against this conclusion, you can find a few of those here: https://psycnet.apa.org/search/citedBy/2020-43548-013

I've been sitting on this for a few months, so dropping these notes here in case someone wants to run with it. Mrienstra (talk) 23:52, 14 December 2023 (UTC)