Talk:Imaginary color

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Edison's questions and suggested merge[edit]

The one reference has a link which does not work. There are some statements in the article that I question. It says that some color sensations in the color space cannot be prodused by mixing primaries, and shows a triangle with 3 primaries. I claim that a spot in the color space outside the triangle could be produced by adding a fourth light. A spectral color or a color more saturated than the desired color, is all that is needed. at a point more saturated than the desired color is all that is needed. This article does not really seem to be needed, and whatever is being put forward here could, if adequately referenced, be incorporated in Color vision as a section. One easy to read reference which discusses supersaturated colors is "Human Information Processing" by Peter Lindsay and Donald Norman, Academic Press, 1972, pp 196-216. P 206 says that if a color stimulus is stared at for a while, the receptors are fatigued. View a saturated green for a while, then view a saturated red, and you perceive an unnaturally supersaturated red.Edison 14:15, 21 May 2007 (UTC)

It says that some color sensations in the color space cannot be prodused by mixing primaries...
Where does it say that? Which color space are you talking about? There's no such thing as "the" color space.
I claim that a spot in the color space outside the triangle could be produced by adding a fourth light.
That may be true (again, depending on which color space you're talking about), but I don't see what it has to do with imaginary colors. As the article says, imaginary colors cannot be produced by light at all.
This comes down to the definition of the word 'produced'. This article is talking about human realizable colors. The horseshoe shaped gamut defines all of the colors that may be possibly seen by a standard observer. This is due to the idea stated near the top of the article, that there is overlap among the cone responses. Thus regardless of the number of lights added, colors outside the gamut can never be distinctly recognized by humans. Adding additional light sources will certainly allow for the creation of different spectral power distributions, but these will not result in a human seeing a different color (see Metamerism). Straha 206th 21:47, 26 June 2007 (UTC)
No, an observer can see supersaturate colors external to the horseshoe as was said above, and per Lindsay and Norman. "Seeing" is a subjective perceptual process in the observer's brain, and not strictly a stimulus property. As for the "standard observer" that was a combined measurement of a number of visual scientists, a mathematical construct. Edison 21:59, 26 June 2007 (UTC)
I will agree that if the receptors are fatigued then a supersaturated color may be perceivable, but this has nothing to do with adding a fourth light source. As for the "standard observer" in my above statements, replace standard observer with "any specific observer". Of course each specific observer will have a slightly different visible color gamut, but it will still be horseshoe shaped and bounded by the monochromatic color curve and the purple line. Adding a fourth light (or fifth, etc) does not produce differently observed colors. This is a result of Grassmanns law which basically implies that because we have a tristimulus visual system, three (properly chosen) light sources is sufficient to produce all normally perceivable colors. Sorry if i wasn't clear, i was only talking about adding additional lights. Another exception to all of this is vision of Tetrachromats, but again that is not really what i'm talking about. Straha 206th 21:03, 27 June 2007 (UTC)
This article does not really seem to be needed, and whatever is being put forward here could, if adequately referenced, be incorporated in Color vision as a section.
You're arguing two different things here: that the article is wrong, and that it should be merged with another article. You should have started two different talk page sections for these.
One easy to read reference which discusses supersaturated colors is "Human Information Processing" by Peter Lindsay and Donald Norman, Academic Press, 1972, pp 196-216.
Neither FSU's library nor the public library has a copy of this book.
View a saturated green for a while, then view a saturated red, and you perceive an unnaturally supersaturated red.
This is a very good point; I was going to put something like it in the article but didn't for lack of a reference. If that book is a reference, please put it in. —Keenan Pepper 16:09, 21 May 2007 (UTC)
The Lindsay and Norman book was widely used in the 1970's and either a college library or public library could get it for you through interlibrary loan, or Amazon can get you a used copy for about $4 with shipping. The website you use as a reference now works for me; I don't know what was wrong with it before. It looks up to date, good and informative, but what is it? Is it a published book which is online? Does it satisfy WP:A? As for "what color space are you talking about" see the lower diagram with three primaries: one looks like spectral red about 700 nm and the other 2 are supersaturated. The coment would apply to the 1931 CIE chromaticity diagram or transforms thereof. Even the set of 1 real and 2 imaginary primaries still fail to cover portions of the CIE color space shown: there are certain hues and saaturations that do not correspond to a mixture of the three. Sometime red, green and blue are used as (real) primaries, and the cover part of whatever color space you are looking at. Other times magenta cyan and yellow are used. Colors which one set of primaries cannot produce may well be produced by the other set. A good photo quality printer may use magenta, light magenta, cyan, light cyan, and yellow, besides gray and black (such color printing is probably neither fully additive nor fully subtractive).Edison 19:47, 21 May 2007 (UTC)
Yeah, that all makes sense to me, but you said you had some problem with the article. What's the problem? —Keenan Pepper 03:27, 22 May 2007 (UTC)
Well, it says "In order for a color space's gamut to contain all real colors, some of the primary colors must be imaginary." But then the lower diagram shows the CIE color space with one real and 2 imaginary primaries and it still fails to reproduce the purples and the saturated blue greens. In other words the imaginary primaries would have to be way outside the color space to reproduce all hues and saturations, or you would need all spectral colors as an infinite number of primaries. The sentence is misleading in that it implies the imaginary primaries shown in the illustration can reproduce all real hues and saturations. Edison 16:41, 22 May 2007 (UTC)
I'd say that the handprint site satisfies WP:A. Its author is a bit opinionated, but references many more technical sources, and has updated his site over the last several years based on comments from experts. He provides a wealth of information about color vision and about watercolor paints. --jacobolus (t) 05:57, 22 May 2007 (UTC)
That says that you like the website, but is it subject to editorial review by someone other than the website owner? I still am looking for info as to who the author is and what the site is. Most personal websites do not satisfy WP:A. Edison 16:35, 22 May 2007 (UTC)
The information on the site relevant to such subjects is all taken from authoritative books on the subject. I don't have access to those, but someone could presumably look them up and cite them. Additionally, there is a great deal of excellent experimental data about watercolor paints, etc., which there is really no reason to doubt, as the author (MacEvoy) has no personal stake in misinforming anyone, and does not make any purchasing recommendations, but rather suggests that his readers experiment for themselves. I don't see any reason to doubt any of the information on the site. In any case, WP:A is not wikipedia policy. As for who the author is, you don't have to look very hard. --jacobolus (t) 00:30, 23 May 2007 (UTC)
It is not up to me to prove he is not a reliable source. Please read WP:A for further details. If he is an authority on color vision, (his site says he earned a PhD in SOMETHING and was a college teacher of something) then his ersonal website might be considered a reliable source on the mathematical details and physiology of vision, more so than if it were just a site created by an artist. Stating thet the books he cites are authoritative does not really promote the site as a reliable source. Once again, I did not see anything at the site to disagree with. Edison 16:54, 23 May 2007 (UTC)
Okay. But there aren't many “authoritative” sources about color vision and color models published online. The handprint site does a great job summarizing and synthesizing many other sources, and is an excellent resource to point users at, if they want somewhere to go for more comprehensive information than is available at Wikipedia. It's probably in the murky edges of WP:A (which is not policy, btw), but I don't think it should be avoided as a source, it certainly should be linked as a place for users to go for more info, particularly in the absence of some Wikipedians going to track down some more “authoritative” sources (not that that would be a bad idea).
In any case, I don't think it's worth worrying about for this article. Nothing in this article is controversial, to the point of necessarily needing a citation at all. --jacobolus (t) 00:21, 24 May 2007 (UTC)

(unindent)As for WP:A not being a policy, note that it is labelled a guideline, and that every day numerous articles are deleted in WP:AFD for failing to meet or for violating guidelines. Material (expecially if controversial) which is not backed by reliable and e and independent sources, or which is original research, runs contrary to WP:A. If reliable sources cannot be found, such material may get deleted. Sometimes articles get deleted and the main reason cited is lack of sources satisfying WP:A. Edison 13:08, 10 June 2007 (UTC)

Merger[edit]

Please comment on the proposed merger at the target article's talk page, Talk:Color vision, in the section "Proposed merger of Imaginary color". To have this article be in any way comprehensible, you need to repeat so much of Color vision that I think it makes more sense to add this as a section to that article. There just does not seem to be enough content here to require a separate article. Edison 19:47, 21 May 2007 (UTC)

No, that's wrong. The article can be perfectly intelligible with a link to color vision, and adding the information that belongs on this article to color vision would just add bloat, and confuse that article. In any case, you should stop adding discussion on this page if you want the discussion to be there. --jacobolus (t) 00:19, 23 May 2007 (UTC)

Utility section[edit]

Because of this little revert war, which I'm not escalating since I follow 1RR, I started rewriting the Utility section, but I gave up. As it is, the section has so many inconsistencies that it's hard to fix without a major revamp:

  1. Use of term "real color" without definition. (Understanding that term is a precondition for understanding imaginary colors.)
  2. Use of term "chromaticity" interchangably with "color" without explanation.
  3. Statement that "additive mixture of two real colors is also a real color" only parenthetical, although most of the section refers to it. Conversely, term "convex" is introduced with prime mention but never used.
  4. There is no logical flow from the introduction of polygon to the place where it is used. In fact, the text first goes (without motivation) back to three primary colors, mentions in passing something about more primary colors, goes back to three, and only after a paragraph break really uses the polygon property, without explicitly referring to it.

I canceled editing because before I invest any more of my time I want to ensure that my edits won't be stubbornly reverted. I belive that editors should take the time to understand good faith changes, and take it from there to further improve Wikipedia. — Sebastian 01:39, 10 June 2007 (UTC)

Hey, thanks for taking my hastily written starter text to pieces. Note that I didn't revert you, and I have no problem with you changing it as radically as you want. I'd love to see your version. —Keenan Pepper 04:17, 10 June 2007 (UTC)
Thank you for your nice reply! I'm sorry that I was a bit grumpy yesterday. I finished the rewrite; please feel free to take it from there. — Sebastian 18:24, 10 June 2007 (UTC)
Looks great as it is now (after Jacobolus tinkered with it). Now we're doing things the wiki way! If anyone wants to replace the image of the ProPhoto gamut with one more appropriate for this article, be my guest. I just used it because you can clearly see that the gamut contains imaginary colors. —Keenan Pepper 20:51, 10 June 2007 (UTC)

Primary colors[edit]

this edit seems to imply that the term "primary color" is used for any (3 or more) colors, as long as they are mixed. So, if I mix e.g three shades of blue, say 460 nm, 470 nm and 480 nm, would they become "primaries" by definition? — Sebastian 19:21, 10 June 2007 (UTC)

That's what I thought. I mean, those three colors would make an surd choice for primaries (the gamut they cover is only a thin sliver of a triangle in the blue corner), but you could technically call them primaries. It might even make sense for aliens whose light-sensing pigments are much more similar to each other than ours are. —Keenan Pepper 20:56, 10 June 2007 (UTC)
This is why I used such a thin sliver, I was erroneously hoping that would make it clear that they would be an absurd choice of primaries. But you had to come up with aliens! ;-) Actually, I just realized that you can even use it here on earth - in false-color images. However, my question was not if any three colors can be used to define a gamut. Of course they can. What I meant was this: Do any three (non-collinear) colors become automatically "primaries", even before anybody thinks about a gamut? Or is that word reserved for colors that have been carefully chosen to optimize their gamut? Maybe the following illustrates what I mean: When you draw three points and connect them, each of the points automatically obtains the name "corner", regardless of what you do with the triangle. The reason why I'm asking is because the current wording "those three colors, which are called primary colors" implies that they automatically become primaries just by virtue of being corners of a triangle. — Sebastian 21:17, 11 June 2007 (UTC)
Every point is a vertex of some triangles and not a vertex of others. Likewise, every color is a primary color for some possible color systems and not a primary color for others. That is, the word primary tells you nothing about the color itself. It only tells you about how the color is used in whatever context you're talking about. —Keenan Pepper 05:32, 12 June 2007 (UTC)
Mhh, I'm not getting my question across. Let's use some non-mathematical examples:
  • Every person is the child of some parents, and not a child of others. But nobody would categorically write "a person is called a child", unless one refers to him or her in that specific relationship.
  • Every street can be considered a step of some driving directions, and not a step of others. But nobody would categorically write "a street is called a step", unless one refers to it in as part of these specific driving directions.
  • Likewise, every corner (or vertex, if you prefer) can of course be considered a primary of some possible color system. But why do we categorically write "[a corner] is called a primary", before we even talk about defining a color system? — Sebastian 07:13, 12 June 2007 (UTC)
To be clear, the point of those colors being "primary" is not that they are part of a triangle, but that the sentence says they are being mixed. So the sentence is basically saying we can mix three "primary" colors to get any color in their triangle. If we mix those colors, and avoid colors outside their gamut, they become the "primaries" of our color mixing model. --jacobolus (t) 01:04, 13 June 2007 (UTC)
Yes, those three blue colors are perfectly reasonable primary colors, just as good as any other set of three (or more or less) primaries. There is absolutely nothing special about being "primary", which is just a label applied to an arbitrary color. Every RGB monitor has different primaries. Different painters have their own preferred primaries, sometimes 6 or 8 or 12 of them. Some printing processes use 6 (hexachrome) or more primaries. All of which are just arbitrary colors that happen to be useful for a particular purpose. --jacobolus (t) 00:52, 13 June 2007 (UTC)
For the third time: Of course they can be used as primaries. I believe that you know more about imaginary colors than I do, but please don't just spool down your knowlege like a record. Please do me the favor and read my question before you answer it. The point of my question is not if three or more colors can be used as primaries. The question is: If you pick three colors and (admittedly, I left that out) mix them, does that already automatically make them primaries?
Here's another, better example: A number of intersecting lines can be used to define a coordinate system, in which case each of them is called an axis. However, that doesn't mean that a line is a priory by definition an axis. It only becomes one when someone decides to use it for a coordinate system. — Sebastian 18:46, 13 June 2007 (UTC)
Yes, for the third time, your question is completely comprehensible, and the answer is the same each time. "Primary color" is a completely arbitrary label, applied to colors that happen to be used to define a coordinate system. There doesn't need to be anything special about it. If (as an example) you pick three colors of paint, and use them to make a painting, by mixing them, then those colors are your primaries. No one is "spooling" anything, and there is no reason to be aggressive about it, and the extra (sarcastic?) emphasis is uncalled for. --jacobolus (t) 09:39, 14 June 2007 (UTC)
Actually, since my responses are apparently unsatisfactory, go read this, and then ask again if your question remains unanswered. The term "primary color" is terribly imprecise, and not particularly useful in my opinion. It is used here in the context of imaginary colors, because "imaginary" "primaries" are used for the corners of RGB color spaces with wide coverage (such as the one pictured).
The explanation given on that page is that, "For painters, a primary color was a pigment color." while for other uses, the definition is slightly different. In computer/video displays, a primary is one of the colors produced by a particular channel (R, G, B, or whatever) at full brightness. In publishing/printing, the primaries are the ink colors used, etc.
It is completely possible to make a painting palette out of only blues, or a computer display out of only blues, or an inkjet printer containing only three different blue color inks. Then those would become your primaries, and the colors which they can mix to produce would become your gamut. Alternately, it's possible to create an idealized, impossible ("imaginary") set of primaries, with which a large gamut can be created.
--jacobolus (t) 09:42, 14 June 2007 (UTC)

Clipping and compression[edit]

The old version mentioned "some clipping or compression must take place". I tried to preserve it, but it has been removed since. That seems like a pertinent topic for an article about imaginary colors. Can anyone elaborate this topic? — Sebastian 21:22, 11 June 2007 (UTC)

As written, it didn't make any sense, so I took it out. What does it mean to be "ruled out"? Any color which is out-of-gamut for the target device will be clipped or compressed, whether it is an "imaginary color" or not. So the statement just confuses the reader without informing him. --jacobolus (t) 22:45, 12 June 2007 (UTC)
I agree that it wasn't very helpful. My intent was not to say that the deleted phrase was instructive, but to point out that the question how models deal with imaginary colors is pertinent to the article, and to ask if someone who knows more about it could add that information. — Sebastian 18:55, 13 June 2007 (UTC)
The article makes that pretty clear already I think. Feel free to improve it though. --jacobolus (t) 09:35, 14 June 2007 (UTC)
Later edit: oh wait, you said "how models deal with" them. The answer to that is that "models" (like L*a*b* or RGB) don't make decisions. It is users of those models who must decide what to do, when converting to the color space used by an output device. So what to do with these colors is defined by the color management software, and the answer is (pretty universally AFAIK) that they are treated identically to any other color outside the gamut of the output space, which is that depending on the rendering intent selected, all of the colors in the image are either compressed or clipped, often by pulling them in towards middle gray in L*a*b* space, or some similar space. --jacobolus (t) 10:24, 14 June 2007 (UTC)

How about some real (!) references...[edit]

The opening statement: "Non-physical, unrealizable, or imaginary colors are combinations of cone cell responses that cannot be produced by any physical light source.[1] " is not supported by the reference. In fact, the phrase "imaginary colors" does not occur at all in the reference.

Re: the statement, "Thus, no object can have an imaginary color, and imaginary colors cannot be seen under normal circumstances." There is the implication that "imaginary" colors can be seen under non-normal circumstances. Please provide a reference verifying this.

Re: the statement, "Therefore, there is no spectral power distribution that excites only green cones without exciting blue or red cones at all, and that situation corresponds to an imaginary color greener than any physical green." Please provide a reference showing that there exist "imaginary colors greener than any physical green." Also, what is a "physical green?" All color is a perception...

Re: "Real colors are colors that can be produced by a physical light source." Sorry, but without an observer, there is no color... and what humans can perceive is defined by XYZ or CIELAB. But I guess the implication is that "imaginary colors are produced by an imaginary light source." Don't think so.

Re: "Therefore, one selects colors outside of the region of real colors as primary colors; in other words, imaginary primary colors. Mathematically, the gamut created in this way contains so-called “imaginary colors”."

No, the primaries are encodings that do not represent real colors, and the gamut contains real colors as well as lots of encodings that do not represent real colors. There are no "imaginary colors" - only encodings that do not correspond to real colors.

Color is a perceptual property. So if you can't see it it's not a color. It is a cognitive perception that is the end result of the excitation of photoreceptors followed by retinal processing and ending in the visual cortex. Colors are defined based on perceptual experiments.

A coordinate in a "colorspace" outside the spectrum locus is not a color. These have occasionally been referred to as "imaginary colors" but this is by and large also erroneous. You can't map an imaginary color from one colorspace to another as the math (and experimental data) for each colorspace breaks down outside the spectrum locus.

There is not one reference cited within this topic that justifies the existence of the topic itself.

There is no mention of "imaginary colors" in such standard references as Hunt's The Reproduction of Color, Lee's Introduction to Color Imaging Science, Fairchild's Color Appearance Models, and Berns' Principles of Color Technology. Even the classic Wyszecki and Stiles Color Science: Concepts and Methods, Quantitative Data and Formulae, 2nd Edition has only a page or so (out of 950) on "imaginary color stimuli."

Colorgeek (talk) 07:21, 8 February 2008 (UTC)

It may well be true that you did not find the topic of this article discussed in four books you looked at. But see the discussion at the top of the page. "Human Information Processing" by Peter Lindsay and Donald Norman, Academic Press, 1972, pp 196-216. P 206 says that if a color stimulus is stared at for a while, the receptors are fatigued. It says that if you view a saturated green for a while, then view a saturated red, you perceive an unnaturally supersaturated red. This is thought to be because the green receptors, being fatigued, no longer send a neural signal to desaturate the red perception from the red receptors. It says "thus the resulting red is more brilliant than can be produced simply by monochromatic light." (p 207) Lindsay and Norman suggest projecting on a screen alternately color negative and positive images of a scene with vivid colors, which would be a good programming challenge for someone to add to the article. 20 seconds of a red circle/blue surround, then 20 seconds of blue circle/red surround, using complementary hues. It is more closely related to receptor fatigue and afterimages than to color reproduction technology. Edison (talk) 14:16, 8 February 2008 (UTC)

Can you provide ANY more recent reference than that? This is speculation. We're talking over 35 years, and a reference that is not widely available. Surely this experiment must have been done by someone by now, and the results published (if true). This should fall right square in the domain of color appearance modeling, yet I've seen no data to back up what is described here. Colorgeek (talk) 15:58, 8 February 2008 (UTC)

A solid reference by highly notable scientists, published by a highly respected publisher, does not have to be in your meighborhood library branch to be "available". You can get it through interlibrary loan, at a good college library or for a few dollars from online second hand booksellers. Please read WP:RS and WP:V which discuss referencing of articles in Wikipedia. The phenomenon was regularly demonstrated in college perception lab classes. Unfortunately I do not at the present time have the access to online journals to find recent research on the topic for you. You are welcome to do your own library research and add references showing that the claimed phenomenon does not occur. I have provided a reference stating that it does occur. Edison (talk) 20:29, 9 February 2008 (UTC)

No one is asking for online references, or condescending attitude. I asked for a *recent* reference that states that "imaginary" colors can be seen by humans under *any* circumstances. This is not widely accepted in color theory circles, and the reference that you cite is dated by more than 35 years. I have a garage full of books that are that old, and some of them are very funny to read now, even though they were written by notable authors and published by well-known scientific publishing houses. The books that I cited earlier are current, definitive references. Color theory has changed a lot in 35 years - from our understanding of the physiology to modeling of color perception (e.g., CIECAM02). Much of what I learned as a PhD grad student in biophysics 15 years ago makes me laugh - and we thought we understood so much back then. If you don't have a current reference, well, then you don't have a current reference. This is why Wikipedia is academic thin-ice. A lot of it is great, and a lot of it is not. There is no formal peer review. User, beware. Colorgeek (talk) 03:12, 10 February 2008 (UTC)

If there is a guideline that says references 35 years old are not considered reliable, I have not seen it. If you find reliable sources stating that it is not possible to perceive a color more saturated than a spectral color, after fatigueing a subset of the receptors, then please add it. Many articles have references far older than 35 years, and these have not been removed or deprecated on account of their being old. The fact that some topic is not addressed in your reference book collection does not by itself disprove a statement of fact in an older book. Do your books deal explicitly with the subjective perception of color saturation in an observer with receptors of one color fatigued? Most books on color reprodduion will be dealing with normal observation conditions. Edison (talk) 19:55, 11 February 2008 (UTC)

Source code for demonstrating "imaginary red"[edit]

For anyone who's interested, here's some Java source code to approximate the effect in the section "Perception of imaginary colors". Maximize the window, position your mouse over the button, and, after 20-30 seconds of staring at the screen, click the button. It looks kind of like magenta to me. « Aaron Rotenberg « Talk « 01:58, 15 March 2008 (UTC)

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
 
import javax.swing.*;
 
public class ColorExperiments extends JFrame {
	public static void main(String args[]) {
		SwingUtilities.invokeLater(new Runnable() {
			public void run() {
				ColorExperiments frame = new ColorExperiments();
				frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
				frame.setVisible(true);
			}
		});
	}
 
	private JPanel contentPanel;
	private JButton changeButton;
	private boolean isRed = false;
 
	public ColorExperiments() {
		setTitle("Color Experiments");
		setSize(640, 480);
 
		contentPanel = new JPanel();
		contentPanel.setLayout(new FlowLayout());
		contentPanel.setBackground(Color.GREEN);
		setContentPane(contentPanel);
 
		changeButton = new JButton();
		changeButton.setText("Change");
		contentPanel.add(changeButton);
		changeButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent arg0) {
				contentPanel.setBackground((isRed = !isRed) ? Color.RED
						: Color.GREEN);
			}
		});
	}
}
Or you could just view two images, one red, one green, in an image slideshow viewer. --Jaded-view (talk) 04:51, 18 May 2008 (UTC)
For example, http://upload.wikimedia.org/wikipedia/commons/thumb/2/29/Solid_green.svg/2000px-Solid_green.svg.png and http://upload.wikimedia.org/wikipedia/commons/thumb/6/62/Solid_red.svg/2000px-Solid_red.svg.png . We loaded each of these into a Firefox tab, hit F11 to maximize the view, stared at the red until it seemed to be just a washed-out orange, and then hit Ctrl-Pgdn to switch to the green tab. Result: HOLY MOLY THAT IS SO GREEN. What this lacks in scientific rigor it more than makes up for with party awesomeness. We also tried green-then-red as specified in the article. This resulted in a hot pink that wasn't nearly as mind-blowing. I cannot recommend this experiment enough. Yes, it's another exciting Friday night at Chez Matuszek (talk) 05:42, 15 January 2011 (UTC).

Another viewable imaginary colour?[edit]

I once read that by viewing a laser with a frequency twice that of green light, the green cones can be stimulated without stimulating the red or blue cones, thus giving the viewer the experience of an incredibly pure green light. I may have misread! David (talk) 18:02, 29 March 2010 (UTC)

That seems unlikely to me. The M and L cones are pretty similar to each-other. Let us know if you can find a source for that though. –jacobolus (t) 19:23, 29 March 2010 (UTC)

Is the disney example really demonstration of an imaginary colour?[edit]

To me, it sounds more like that old optical illusion where a checkerboard has a shadow thrown on it, such that the same middle shade of gray looks darker and lighter depending on whether it's surrounded by bright or by dark colours. As in, the grass looks greener because it's more different from pink, than because the pink is fatiguing your red and blue receptors. --122.106.155.219 (talk) 08:34, 30 March 2011 (UTC)

I don't think the article actually claims the disney color is “imaginary”, but you’re probably right that the better place for the Epcot factoid is an article about simultaneous contrast. –jacobolus (t) 14:41, 30 March 2011 (UTC)

I don't believe it's entirely in regards to seeing the pavement with an exact complimentary color to that of the grass purely for making the colors more vivid. What is also true is that the afterimage of looking at the pavement when walking around and in one's peripheral will bring out the color of the grass by fatiguing the red photoreceptors so that when the grass is viewed it is experienced as a more vivid hue. –WisdomFromIntrospect (t) 09:55, 07 July 2011 (UTC)