It's hard to compress what's known about the subject of color perception differences among people with nominally normal color vision.
Hypothetical tetrachromacy has been demonstrated, that is, M and L cones with minor differences in peak spectral response existing in a retinal mosaic. The question arises whether this difference is capable of being propagated through the bipolar connecting neuronal paths (which form the "blue-yellow" and "red-green" channel paths conveying color info to the brain visual cortex).
Several studies found no evidence for a "fourth channel", and some perceptual studies did not show confirmation of tetrachromacy. However a couple of studies do hint at rare female subjects who do seem to have good evidence for this trait.
It is postulated that because of the differences in the exact genetic encodings on the 2 X chromosomes in females, that up to 50% of women have a retinal mosaic of 4 populations of cones, S M M' L, S M L L', and so on. The theory is that this allowed greater distinction of yellow to red color distinction which may have helped survival by avoiding toxic plants based on subtle color distinctions.
In art, there are great colorists and those who are virtually incapable of subtle use of color. If anyone interested in finding out about their own abilities, check out:
http://www.xrite.com/online-color-test-challenge
The on-line test is only a rough estimate, but it's fun and challenging. I suspect there's a spectrum, aka normal distribution of color discrimination ability. I should't say how well I did, though the results of trying it several times were remarkably consistent despite different computer systems that I used.
BTW I encountered one very intriguing article reporting on a large sample of retinas obtained post-mortem. As expected, ~50% of females showed retinal mosaic of 2 M or L cones where only one each was expected. Most fascinating was the fact that of male retinas 8% showed a similar tetrachromat pattern. How that could arise is a mystery considering males have only one X chromosome. (There are pigment gene variations with greater number of CNV and TR which could be activated? But it's still a mystery.)
> Hypothetical tetrachromacy has been demonstrated, that is, M and L cones with minor differences in peak spectral response existing in a retinal mosaic. The question arises whether this difference is capable of being propagated through the bipolar connecting neuronal paths (which form the "blue-yellow" and "red-green" channel paths conveying color info to the brain visual cortex).
Adding genes for extra cone types into normally dichromatic mammals (mice or something? I don’t remember off hand and I don’t have the citation at my fingertips) has seemed in studies to result in trichromatic vision, so it’s not too big a leap to suspect that tetrachromacy of the type described in the article might happen for some humans.
As you say there hasn’t been any study which showed this conclusively (that I’ve seen anyhow). I’d love to see more thorough research on these subjects who supposedly possess such vision.
> In art, there are great colorists and those who are virtually incapable of subtle use of color. If anyone interested in finding out about their own abilities, check out:http://www.xrite.com/online-color-test-challenge
Note, this online test is a bit easier than the paper version of the Farnsworth–Munsell hue test, since the colors in the screen version end up with some lightness differences that make it a bit easier to keep some sections of the chart in order. Either way, the test IMO mostly measures (a) whether someone has “normal” trichromatic vision, and (b) how patient and willing to fiddle with fine details they are. I don’t personally think Farnsworth–Munsell test scores are super meaningful, though a very poor score does indicate some color vision deficiency. [FWIW, if I take the time to do the test slowly, either on screen or on paper, I consistently score ~0, occasionally mixing up one pair or another.]
But anyway, I think the ability to be a good colorist in art has a whole lot to do with practice. Spending a lot of time mixing paint or color correcting photographs is likely to heighten awareness of tiny distinctions. For instance, I know that after a couple years of photography courses, several of my friends got much better at noticing color casts in photographs. Not that they couldn’t physically see them before, but after experience they more often spontaneously noticed the casts and started to have a feel for just how much adjustment in which direction would be necessary to counteract them.
I suspect there's a spectrum [of color perception among people with nominally normal color vision].
Indeed there is. The most common is a variant carried by around 2/3 of the human population (depending on ethnicity and gender), which results in a slightly different red response curve, as shown in color matching tests [1]; and might also be involved in some forms of actual color blindness. Other, less common variations involve mosaicism of both red and green pigments as well [see ibid, Fig. 8].
The tetrachromacy thing is a perennial media favorite these days; but IMO these subtler but actually widespread differences are much more interesting, at least from a philosophy of mind point of view.
[1] Deeb 2005 - The molecular basis of variation in human color vision. Link below:
But does that really mean I got all of them correct?! I was squinting and squinting (and cursing insertion sort), and I was pretty tired out near the end. I thought I might've been able to squeeze out some last tiny errors if I would have gone over all those bars again, flipping a few boxes that were not just quite right.
Also if I look at the rainbow bar in the screenshot, I'm assuming that's the full range of colours I sorted, I can clearly see there's a few errors and discontinuities in there still.
I wonder if it maybe just rounds down really small errors to zero because they're "close enough"? That's too bad, because I'm tempted to go back and try to do better :) But if it won't increase my score (decrease my error rate), I only have my own judgement of that final full rainbow hue bar to go by :)
(also, remember to disable Flux/Redshift. it probably doesn't help accuracy :) )
"considering males have only one X chromosome": Around 1 in 500 males have two X chromosomes (XXY), so it should be possible for males to end up as tetrachromats too (although this wouldn't explain 8%). See https://en.wikipedia.org/wiki/Klinefelter_syndrome
Antico's painting of an eucalyptus doesn't "give us a hint of the extra shades she is seeing". It's just another instance of the [El Greco fallacy](http://www.huffingtonpost.com/wray-herbert/a-new-look-at-per...): art historians used to think that El Greco's elongated figures were a result of his having a severe form of astigmatism. But, of course, if that had been the reason, he would have also seen an elongated canvass when painting, with the net result of figures painted in standard proportions.
Here as well, if the tree painting was somewhow a reflection of Antico's tetrachromatism, she would have chosen colors that matched those that she sees on the eucalyptus. Such colors would be indistinguishable to us trichromats from the colors the tree does have, with the net result of a normally colored tree painting.
At best, Antico is using something of a metaphor to convey her tetrachromatism. But no real insight on her vision.
I'm a printmaker (among other things), mostly making monotypes in recent years. The technique allows subtle color transitions which I deeply enjoy, and I notice particular pleasure of the visual effects of colors that range from green, yellow-green through orange and red.
I've discovered that many art colleagues "don't get it", i.e., who seem not to discern the same subtleties that I appreciate. I'm beginning to think this may be due to differences in color discrimination. IOW whatever the basis for the difference I'm sure it would be measurable within limits of color vision test resolution.
I don't know about the illustration in the article. Reproduction (especially reduced resolution) may very well coarsen the color so that the distinctions are run together, so no difference to see. You might want to try the on-line Farnswell-Munsell 100 test alluded to above which might be more informative.
I think it's different: You can see the color green in multiple ways: Monochromatic light of 520nm wavelength looks green to you, but so does dicromatic light composed of a mixture of yellow (580nm) and blue (440nm). The two situations activate your 3 cone cells in the same way.
When painting, you might 'see' the 520nm green in your scene, but choose paint that is a mixture of yellow and blue to recreate it since the net color looks the same to you. However, the paint will look different from the scene to someone missing (eg) red cones.: Your red cones contributed to the blue+yellow looking green to you, since the yellow paritally activates the red cones.
Your point is valid, and while I agree there is not strong enough evidence for a causal connection, I think the idea is interesting.
My mother has painted Impressionist-style oil paintings my whole life, and taught painting classes. In her classes, she always tells people to use colors that they don't see ("You need the pink on the water", etc). Once you've painted enough, you learn to realize what colors are in the scene but not quite obvious. You definitely exaggerate the colors ("hint of pink" becomes "pink streaks") while painting in this style, but it also forces you to think harder about what colors your eye actually sees.
So it seems to me that impressionist-style coloring can definitely come from "faking it" (being taught it, and trying hard), but I would definitely believe it could come from tetrachromism, where those small differences stick out to you a lot. It would be fascinating to know if any early impressionists had evidence of being tetrachromatic.
what about the "night vision" painting. if it's pitch black and someone has the ability to see a vase, and then remembers the vase and paints the vase green in another room brightly lit...
well, they wouldn't paint a pitch black canvas and claim they can see a vase in that painting.
if el greco had some kind of condition that made him see elongated figures at thirty feet away, would a small normally proportioned figure drawing two feet away really look elongated also?
I'm from Australia but hadn't heard of the Rainbow Eucalypt before (the tree that the featured tetrachromat painted). That's not so unlikely as there are a lot of Eucalyptus species.
Still, I was curious and so looked it up and was very interested to find that it is a Eucalypt from outside Australia and, more than that, the only one whose native region partly lies within the northern hemisphere. Another name for it is the Mindanao gum, as it is native to the tropical rainforests of Mindanao in the Philippines (north of the equator).
From my photography experience I noticed a lot more abnormalities than just tetrachromacy, which is not uncommon amongst artists. I had a model that was "seeing" colors in the sounds (synaesthesia) - she was often saying you talk to me in blue or that person has such a nice white voice.
I've been tested for color vision and I am 100% accurate meaning I can discern subtle shades from each other precisely with no effort. I also have a very light form of synaesthesia manifesting itself by seeing a flash of light in the night right before an unexpected sudden loud noise (yet with observable latency) - like seeing a lightning just before hearing a thunder, even if the noise is not accompanied by any light.
I was also always wondering if what I perceive as "blue" is the same as other people perceive as "blue"? What if the neural response in my brain wires the color sensation in the same way as other people perceive "green"? That would help to understand individual preferences for colors. Also, we know there are special cells in retina doing direction detection, edge detection etc. - what if this had a profound impact on how we individually perceive world around us? Somebody can have a strong edge or directional detection present in their view all the time, logically assuming it's normal for the others as well that are lacking that ability. We are just too diverse, and people are rather quiet in order not to risk being considered abnormal and marginalized, a common problem for artists in general.
I once had a friend, over some beers, describe his synaesthesia. He thought it was just him being crazy, until I handed him my phone with the Wikipedia page on it.
He said that people who were being dishonest sounded purple- the man was a walking lie detector, and never knew how he was doing it.
Do you also see a pattern in the white flash (zebra stripes, lines, checkers)? I always assumed that was a normal side-effect of being startled while resting; changing from your brain-vision to eye-vision, though I'm not sure of the patterns significance.
Mantis Shrimps have 12 photoreceptors, they can also see in all polarisations. They don't do paintings so it's hard to know how they experience this. http://en.wikipedia.org/wiki/Mantis_shrimp#Eyes
It's not that they see a few colors that no one perceives, it's that for them color is a 4 dimensional space instead of a 3 dimensional one. So it's a whole new world of different colors.
Even though our eyes detect color in 3 dimensional space, that doesn't seem to be how we perceive it. E.g. I can't tell you how much red, green, or blue is in a color, just that it's close to the cluster of colors I recognize as "purple" or "blue" or "orange" or whatever.
There was a good study published recently documenting the ability for patients with eye surgery who could see into the UV spectrum.
The cornea blocks some UV light so if you have eye correction surgery your cornea is now modified/thinner and you can see slightly into the UV spectrum.
Probably has some downsides too.. Cataracts are probably more probable seeing as people tend to get them more frequently at higher altitude.
The Tibetan people apparently have a high rate of cataracts since there is higher UV light at the higher altitude.
It wasn't the cornea, but an artificial lens that was responsible. [0] UV passed through the artificial lens, but not through our natural one. It was replaced because of cataracts.
The thing is, the woman doesn't seem to perceive new colors that other people do not; the colors others don't see are being aliased to familiar colors like "pink", and "red". (When she says "do you see that pink", is it a pink that we could see elsewhere? Or some color that we have no concept of, but which she relates to pinkness.)
I'd be curious if she still sees the same thing in a digital image of the scene, or does the RGB system destroy it.
Also of interest is that birds have little oil droplets, often colored, as part of their visual set up. There are five different known types of color-filtering oil droplets (a sixth that is transparent) but it doesn't appear every bird has all of them.
I'm no bird sight expert but it's suggested here [0] that a particular bird may have 8 effective color receptors (5 cones, 3 cone-droplet pairs) for a huge number of colors humans can't see. Diagrams of the receptors themselves can be found at the wiki [1].
It's learnable and takes a lot of practice mixing colors and you need the right teacher. I picked up this ability in art school and it absolutely makes a sunset more beautiful. But to keep seeing this way you have to practice regularly. Use it or lose it. If I'm not painting regularly, it's gone.
Like if you play chess for hours and hours every day, eventually you start to experience everything in terms of chess moves. It's the same with color. Look at just about any flat surface long enough and you'll notice it has a hue, saturation and value. Just go into Photoshop and you'll see that boring white wall has variations in hue, saturation and value, it's no medical mystery in my opinion.
This part is a tiny more green, that part is a tiny more blue. I'm not giving you an art lesson here but you get the idea. Artists know they can make things look farther away by painting them blue/gray, decrease saturation with distance, etc. The painter learns to exaggerate because she just has a 2D surface to work with. Anyway, through the process of painting our perception of color improves, even when we're not painting.
K-12 the goal is just paint the sky blue and the grass green, color inside the lines and get your grade. But if you want to be a serious painter at some point, you may want to look at things fresh, more intently. When people see your paintings, don't expect them to care how long it took to mix the color. Only a few artists will notice and they're not the ones buying your work.
So even for artists, seeing color is not terribly useful, because mixing color is very time-consuming. It's more a hindrance than anything because I can finish an ink wash in 1/100th the time and sell that for the same price as an oil painting of the same subject.
If you have all the time in the world and don't need money, I say go for it, buy some expensive oil paint and send me an email, I'll tell you what to buy. Stretch the canvas yourself and go all out.
> Jordan’s “acid test” involved coloured discs showing different mixtures of pigment, such as a green made of yellow and blue. The mixtures were too subtle for most people to notice: almost all people would see the same shade of olive green, but each combination should give out a subtly different spectrum of light that would be perceptible to someone with a fourth cone.
From what I understand, a modern monitor is capable of displaying the entire range of colors perceptible to the human eye. Am I mistaken about that?
So would it not be possible to create a web-based version of these "coloured discs", and then we can test ourselves.
> From what I understand, a modern monitor is capable of displaying the entire range of colors perceptible to the human eye. Am I mistaken about that?
It kinda depends on what you think as a color. Computer monitors rely heavily on that (normal) human vision can not distinguish from eg. red-green and "true"[1] yellow, even though they are completely different from physical perspective. So a typical computer monitor does not bother to create "true" yellow and instead cheats by outputting red-green when asked for yellow.
If we had an hypothetical tetrachromat with additional cones sensitive for yellow light, her color vision would span the same range as normal (trichromat) color vision, ie cover the same piece of EM spectrum. But normal computer monitors would not be able to reproduce for her what she sees in real world.
Then there is the somewhat related discussion about violet and red-blue which is quite curious when you begin think about it.
[1] I'm using "true" color to refer light with specific wavelength
From a purely physical point of view, a computer monitor can only produce a spectrum of light (photon histogram) that has spikes on the wavelengths for red, green and blue. These spectra reproduce the vast majority of colors that are perceptible to humans with normal vision. However, the "colored discs" in the article exploit the fact that two colors that are perceived as identical, can in fact be produced by (at least) two different spectra of light. Tetracromats can differentiate between some of these spectra, whereas people with normal vision can not.
(A simple example: The color cyan can be produced by additively combining the spectra of blue and green, but can also be produced by creating photons with only the wavelength of cyan, 490-520nm according to Wikipedia. A person with normal color vision would not be able to differentiate between these two light sources, whereas a measurement device or perhaps a tetrachromat could. A computer monitor can only produce the first of these).
So the answer to your question is no, unfortunately.
Look at this image (http://upload.wikimedia.org/wikipedia/commons/thumb/6/60/CIE...) from Wikipedia. It represents all the colors (chromaticities) that humans can see. A device that reproduces images using primary colors can reproduce all the colors within the vertices of the primaries used. For example, an RGB monitor can reproduce all colors within the triangle formed by the particular R, G, and B subpixel primaries as plotted on that diagram.
What you'll notice though is that because the diagram has a curved edge (this is the spectrum of visible light actually), no polygon can encompass all colors.
I've always thought it would be cool if someone made a CRT using two prisms (splitting light from a blackbody), such that a narrowband of light from one prism is combined with a narrowband of light from the other prism in different intensities. This would be able to reproduce all colors a human can see, assuming the ability to tune to a specific portion of the spectrum is fast enough to scan over all pixels that constitute the image.
Without using a monitor, a potential test would be to look at flowers like Rudbeckias(in real life of course) that have evolved to have patterns that tetrachromat insects can see. If you can see these patterns, you may be a tetrachromat.
> The crux of Jordan’s argument lay in the fact that the gene for our red and green cone types lies on the X chromosome. Since women have two X chromosomes, they could potentially carry two different versions of the gene, each encoding for a cone that is sensitive to slightly different parts of the spectrum. In addition to the other two, unaffected cones, they would therefore have four in total – making them a “tetrachromat”.
Why couln't this happen for either of the other cones?
The male equivalent is "Anomalous trichromacy" http://en.wikipedia.org/wiki/Color_blindness#Anomalous_trich.... You have one of the color receptors tuned to a slightly different frequency, so you see the word in a different way. (Which way is the correct way?) This condition is easy to spot with the standard Ishihara color test, so it's easy to measure the % of the population in these cases.
--- Green
The most common case of male anomalous trichromacy is the "wrong/unusual" green receptor case, so the most common case of woman tetracromat is one that has 2 copies of the usual blue receptor, 2 copies of the usual red receptor and 1 copy of the usual green receptor 1 copy of the unusual green receptor. This is the case discussed in the article.
To reduce the text size I'll denote this kind of tetracromat with BBGgRR, where the capital letter denote the usual color receptor and the noncapital letter denote the unusual color receptor. (This is unrelated to recessive and dominant genes that are usually denoted by capital and noncapital letters.)
--- Red
The second most common case of male anomalous trichromacy is the "wrong/unusual" red receptor case, so the seccond most common case of woman tetracromat is BBGGRr (1 copy of the usual red receptor an 1 copy of the unusual red receptor).
Obviously, you can have both mixed copies, so a woman can have BBGgRr and be a pentacromat. At least have the genes to "see" in a 5-dimensional color space. If she can use this ability is less clear.
--- Blue
The least common case of male anomalous trichromacy is the "wrong/unusual" blue receptor case, so the least common case of woman tetracromat is BbGGRR.
It can be mixed with the other cases, so a woman can be pentacromat or hexacromat.
The interesting part is that the blue gene is not in the X chromosome, so both male and females have two copies. So a male can be tetracromat BbG_R_ . But this chromosome is not inactivated as the 50% of the X chromosomes in females. So I'm not sure if it's possible to have a different kind of vision in this case.
--- It's more complicated
Actually you can have more than 1 copy of the color genes in each chromosome, and there are more than two variations of each gene, so it's more complicated.
The gene for the “short” wavelength cone† is located on chromosome 7, whereas the genes for the others are located on the X chromosome. Since females have two X chromosomes, it is possible for them to have 2 variant copies of the long or medium cone genes. (Since males only have one X chromosome, color vision deficiencies caused by a missing or abnormal copy of one of the medium/long cone pigment genes are much more common than for females.)
It would certainly be possible for a genetic mutation to result in an extra mutated copy of the short cone pigment gene, but I don’t think I’ve heard of variants of this gene with slightly different light sensitivity than the usual type (they might exist though?). By contrast “non-standard” version of the medium cone pigment gene is relatively common.
† We should properly refer to the cones as long, medium, and short rather than red, green, and blue, since color is computed from differences in cone responses.
The frequency sensitivity curve of rods is different from reach of the cone types, too. If some rods contribute to daylight vision, then everyone is tetrachromatic to some extent.
[+] [-] jrapdx3|11 years ago|reply
Hypothetical tetrachromacy has been demonstrated, that is, M and L cones with minor differences in peak spectral response existing in a retinal mosaic. The question arises whether this difference is capable of being propagated through the bipolar connecting neuronal paths (which form the "blue-yellow" and "red-green" channel paths conveying color info to the brain visual cortex).
Several studies found no evidence for a "fourth channel", and some perceptual studies did not show confirmation of tetrachromacy. However a couple of studies do hint at rare female subjects who do seem to have good evidence for this trait.
It is postulated that because of the differences in the exact genetic encodings on the 2 X chromosomes in females, that up to 50% of women have a retinal mosaic of 4 populations of cones, S M M' L, S M L L', and so on. The theory is that this allowed greater distinction of yellow to red color distinction which may have helped survival by avoiding toxic plants based on subtle color distinctions.
In art, there are great colorists and those who are virtually incapable of subtle use of color. If anyone interested in finding out about their own abilities, check out: http://www.xrite.com/online-color-test-challenge
The on-line test is only a rough estimate, but it's fun and challenging. I suspect there's a spectrum, aka normal distribution of color discrimination ability. I should't say how well I did, though the results of trying it several times were remarkably consistent despite different computer systems that I used.
BTW I encountered one very intriguing article reporting on a large sample of retinas obtained post-mortem. As expected, ~50% of females showed retinal mosaic of 2 M or L cones where only one each was expected. Most fascinating was the fact that of male retinas 8% showed a similar tetrachromat pattern. How that could arise is a mystery considering males have only one X chromosome. (There are pigment gene variations with greater number of CNV and TR which could be activated? But it's still a mystery.)
[+] [-] jacobolus|11 years ago|reply
Adding genes for extra cone types into normally dichromatic mammals (mice or something? I don’t remember off hand and I don’t have the citation at my fingertips) has seemed in studies to result in trichromatic vision, so it’s not too big a leap to suspect that tetrachromacy of the type described in the article might happen for some humans.
As you say there hasn’t been any study which showed this conclusively (that I’ve seen anyhow). I’d love to see more thorough research on these subjects who supposedly possess such vision.
> In art, there are great colorists and those who are virtually incapable of subtle use of color. If anyone interested in finding out about their own abilities, check out: http://www.xrite.com/online-color-test-challenge
Note, this online test is a bit easier than the paper version of the Farnsworth–Munsell hue test, since the colors in the screen version end up with some lightness differences that make it a bit easier to keep some sections of the chart in order. Either way, the test IMO mostly measures (a) whether someone has “normal” trichromatic vision, and (b) how patient and willing to fiddle with fine details they are. I don’t personally think Farnsworth–Munsell test scores are super meaningful, though a very poor score does indicate some color vision deficiency. [FWIW, if I take the time to do the test slowly, either on screen or on paper, I consistently score ~0, occasionally mixing up one pair or another.]
But anyway, I think the ability to be a good colorist in art has a whole lot to do with practice. Spending a lot of time mixing paint or color correcting photographs is likely to heighten awareness of tiny distinctions. For instance, I know that after a couple years of photography courses, several of my friends got much better at noticing color casts in photographs. Not that they couldn’t physically see them before, but after experience they more often spontaneously noticed the casts and started to have a feel for just how much adjustment in which direction would be necessary to counteract them.
[+] [-] gone35|11 years ago|reply
Indeed there is. The most common is a variant carried by around 2/3 of the human population (depending on ethnicity and gender), which results in a slightly different red response curve, as shown in color matching tests [1]; and might also be involved in some forms of actual color blindness. Other, less common variations involve mosaicism of both red and green pigments as well [see ibid, Fig. 8].
The tetrachromacy thing is a perennial media favorite these days; but IMO these subtler but actually widespread differences are much more interesting, at least from a philosophy of mind point of view.
[1] Deeb 2005 - The molecular basis of variation in human color vision. Link below:
http://www.mbfys.ru.nl/staff/j.vangisbergen/endnote/endnotep...
[+] [-] tripzilch|11 years ago|reply
But does that really mean I got all of them correct?! I was squinting and squinting (and cursing insertion sort), and I was pretty tired out near the end. I thought I might've been able to squeeze out some last tiny errors if I would have gone over all those bars again, flipping a few boxes that were not just quite right.
Also if I look at the rainbow bar in the screenshot, I'm assuming that's the full range of colours I sorted, I can clearly see there's a few errors and discontinuities in there still.
I wonder if it maybe just rounds down really small errors to zero because they're "close enough"? That's too bad, because I'm tempted to go back and try to do better :) But if it won't increase my score (decrease my error rate), I only have my own judgement of that final full rainbow hue bar to go by :)
(also, remember to disable Flux/Redshift. it probably doesn't help accuracy :) )
[+] [-] kens|11 years ago|reply
[+] [-] judk|11 years ago|reply
Doesn't work on mobile :-(
[+] [-] Schiphol|11 years ago|reply
Here as well, if the tree painting was somewhow a reflection of Antico's tetrachromatism, she would have chosen colors that matched those that she sees on the eucalyptus. Such colors would be indistinguishable to us trichromats from the colors the tree does have, with the net result of a normally colored tree painting.
At best, Antico is using something of a metaphor to convey her tetrachromatism. But no real insight on her vision.
[+] [-] jrapdx3|11 years ago|reply
I've discovered that many art colleagues "don't get it", i.e., who seem not to discern the same subtleties that I appreciate. I'm beginning to think this may be due to differences in color discrimination. IOW whatever the basis for the difference I'm sure it would be measurable within limits of color vision test resolution.
I don't know about the illustration in the article. Reproduction (especially reduced resolution) may very well coarsen the color so that the distinctions are run together, so no difference to see. You might want to try the on-line Farnswell-Munsell 100 test alluded to above which might be more informative.
[+] [-] ealloc|11 years ago|reply
When painting, you might 'see' the 520nm green in your scene, but choose paint that is a mixture of yellow and blue to recreate it since the net color looks the same to you. However, the paint will look different from the scene to someone missing (eg) red cones.: Your red cones contributed to the blue+yellow looking green to you, since the yellow paritally activates the red cones.
[+] [-] clay_to_n|11 years ago|reply
My mother has painted Impressionist-style oil paintings my whole life, and taught painting classes. In her classes, she always tells people to use colors that they don't see ("You need the pink on the water", etc). Once you've painted enough, you learn to realize what colors are in the scene but not quite obvious. You definitely exaggerate the colors ("hint of pink" becomes "pink streaks") while painting in this style, but it also forces you to think harder about what colors your eye actually sees.
So it seems to me that impressionist-style coloring can definitely come from "faking it" (being taught it, and trying hard), but I would definitely believe it could come from tetrachromism, where those small differences stick out to you a lot. It would be fascinating to know if any early impressionists had evidence of being tetrachromatic.
[+] [-] tcgv|11 years ago|reply
1) Considering that a tetrachromatic colour X is seen by regular folks as a trichromatic colour Y.
Then:
2) Are all artificial representations (paint) of the tetrachromatic colour X also seen by regular folks as the trichromatic colour Y?
I guess your hypothesis is true only if the answer to the above question is "yes".
[+] [-] javert|11 years ago|reply
Antico may see some color in the bark that I don't see---say, green.
So she adds actual green paint into her painting, which, of course, I do see.
[+] [-] jrs99|11 years ago|reply
well, they wouldn't paint a pitch black canvas and claim they can see a vase in that painting.
if el greco had some kind of condition that made him see elongated figures at thirty feet away, would a small normally proportioned figure drawing two feet away really look elongated also?
[+] [-] oska|11 years ago|reply
Still, I was curious and so looked it up and was very interested to find that it is a Eucalypt from outside Australia and, more than that, the only one whose native region partly lies within the northern hemisphere. Another name for it is the Mindanao gum, as it is native to the tropical rainforests of Mindanao in the Philippines (north of the equator).
http://en.wikipedia.org/wiki/Eucalyptus_deglupta
[+] [-] bitL|11 years ago|reply
I've been tested for color vision and I am 100% accurate meaning I can discern subtle shades from each other precisely with no effort. I also have a very light form of synaesthesia manifesting itself by seeing a flash of light in the night right before an unexpected sudden loud noise (yet with observable latency) - like seeing a lightning just before hearing a thunder, even if the noise is not accompanied by any light.
I was also always wondering if what I perceive as "blue" is the same as other people perceive as "blue"? What if the neural response in my brain wires the color sensation in the same way as other people perceive "green"? That would help to understand individual preferences for colors. Also, we know there are special cells in retina doing direction detection, edge detection etc. - what if this had a profound impact on how we individually perceive world around us? Somebody can have a strong edge or directional detection present in their view all the time, logically assuming it's normal for the others as well that are lacking that ability. We are just too diverse, and people are rather quiet in order not to risk being considered abnormal and marginalized, a common problem for artists in general.
[+] [-] mabbo|11 years ago|reply
He said that people who were being dishonest sounded purple- the man was a walking lie detector, and never knew how he was doing it.
[+] [-] weesals|11 years ago|reply
[+] [-] im3w1l|11 years ago|reply
Does this improve your reaction time to sudden noises? You should totally test it :)
[+] [-] emsy|11 years ago|reply
[+] [-] jimmytidey|11 years ago|reply
[+] [-] joelthelion|11 years ago|reply
[+] [-] Houshalter|11 years ago|reply
See this chart for example: http://imgs.xkcd.com/blag/satfaces_map_1024.png
Interestingly there is some evidence that culture and language might affect our perception of color.
[+] [-] burtonator|11 years ago|reply
The cornea blocks some UV light so if you have eye correction surgery your cornea is now modified/thinner and you can see slightly into the UV spectrum.
Probably has some downsides too.. Cataracts are probably more probable seeing as people tend to get them more frequently at higher altitude.
The Tibetan people apparently have a high rate of cataracts since there is higher UV light at the higher altitude.
[+] [-] glabifrons|11 years ago|reply
[0] http://science.slashdot.org/story/12/02/14/165202/followup-u...
[+] [-] kazinator|11 years ago|reply
I'd be curious if she still sees the same thing in a digital image of the scene, or does the RGB system destroy it.
[+] [-] cjo|11 years ago|reply
I'm no bird sight expert but it's suggested here [0] that a particular bird may have 8 effective color receptors (5 cones, 3 cone-droplet pairs) for a huge number of colors humans can't see. Diagrams of the receptors themselves can be found at the wiki [1].
[0] - http://watchingtheworldwakeup.blogspot.com/2008/11/mountain-... [1] - http://en.wikipedia.org/wiki/Bird_vision#Light_perception
[+] [-] pjbrunet|11 years ago|reply
Like if you play chess for hours and hours every day, eventually you start to experience everything in terms of chess moves. It's the same with color. Look at just about any flat surface long enough and you'll notice it has a hue, saturation and value. Just go into Photoshop and you'll see that boring white wall has variations in hue, saturation and value, it's no medical mystery in my opinion.
This part is a tiny more green, that part is a tiny more blue. I'm not giving you an art lesson here but you get the idea. Artists know they can make things look farther away by painting them blue/gray, decrease saturation with distance, etc. The painter learns to exaggerate because she just has a 2D surface to work with. Anyway, through the process of painting our perception of color improves, even when we're not painting.
K-12 the goal is just paint the sky blue and the grass green, color inside the lines and get your grade. But if you want to be a serious painter at some point, you may want to look at things fresh, more intently. When people see your paintings, don't expect them to care how long it took to mix the color. Only a few artists will notice and they're not the ones buying your work.
So even for artists, seeing color is not terribly useful, because mixing color is very time-consuming. It's more a hindrance than anything because I can finish an ink wash in 1/100th the time and sell that for the same price as an oil painting of the same subject.
If you have all the time in the world and don't need money, I say go for it, buy some expensive oil paint and send me an email, I'll tell you what to buy. Stretch the canvas yourself and go all out.
[+] [-] shutupalready|11 years ago|reply
From what I understand, a modern monitor is capable of displaying the entire range of colors perceptible to the human eye. Am I mistaken about that?
So would it not be possible to create a web-based version of these "coloured discs", and then we can test ourselves.
[+] [-] zokier|11 years ago|reply
It kinda depends on what you think as a color. Computer monitors rely heavily on that (normal) human vision can not distinguish from eg. red-green and "true"[1] yellow, even though they are completely different from physical perspective. So a typical computer monitor does not bother to create "true" yellow and instead cheats by outputting red-green when asked for yellow.
If we had an hypothetical tetrachromat with additional cones sensitive for yellow light, her color vision would span the same range as normal (trichromat) color vision, ie cover the same piece of EM spectrum. But normal computer monitors would not be able to reproduce for her what she sees in real world.
Then there is the somewhat related discussion about violet and red-blue which is quite curious when you begin think about it.
[1] I'm using "true" color to refer light with specific wavelength
[+] [-] marvin|11 years ago|reply
(A simple example: The color cyan can be produced by additively combining the spectra of blue and green, but can also be produced by creating photons with only the wavelength of cyan, 490-520nm according to Wikipedia. A person with normal color vision would not be able to differentiate between these two light sources, whereas a measurement device or perhaps a tetrachromat could. A computer monitor can only produce the first of these).
So the answer to your question is no, unfortunately.
[+] [-] Xcelerate|11 years ago|reply
What you'll notice though is that because the diagram has a curved edge (this is the spectrum of visible light actually), no polygon can encompass all colors.
I've always thought it would be cool if someone made a CRT using two prisms (splitting light from a blackbody), such that a narrowband of light from one prism is combined with a narrowband of light from the other prism in different intensities. This would be able to reproduce all colors a human can see, assuming the ability to tune to a specific portion of the spectrum is fast enough to scan over all pixels that constitute the image.
[+] [-] sigterm|11 years ago|reply
[+] [-] TheSpiceIsLife|11 years ago|reply
[+] [-] mamoswined|11 years ago|reply
[+] [-] philh|11 years ago|reply
Why couln't this happen for either of the other cones?
[+] [-] gus_massa|11 years ago|reply
--- Green
The most common case of male anomalous trichromacy is the "wrong/unusual" green receptor case, so the most common case of woman tetracromat is one that has 2 copies of the usual blue receptor, 2 copies of the usual red receptor and 1 copy of the usual green receptor 1 copy of the unusual green receptor. This is the case discussed in the article.
To reduce the text size I'll denote this kind of tetracromat with BBGgRR, where the capital letter denote the usual color receptor and the noncapital letter denote the unusual color receptor. (This is unrelated to recessive and dominant genes that are usually denoted by capital and noncapital letters.)
--- Red
The second most common case of male anomalous trichromacy is the "wrong/unusual" red receptor case, so the seccond most common case of woman tetracromat is BBGGRr (1 copy of the usual red receptor an 1 copy of the unusual red receptor).
Obviously, you can have both mixed copies, so a woman can have BBGgRr and be a pentacromat. At least have the genes to "see" in a 5-dimensional color space. If she can use this ability is less clear.
--- Blue
The least common case of male anomalous trichromacy is the "wrong/unusual" blue receptor case, so the least common case of woman tetracromat is BbGGRR.
It can be mixed with the other cases, so a woman can be pentacromat or hexacromat.
The interesting part is that the blue gene is not in the X chromosome, so both male and females have two copies. So a male can be tetracromat BbG_R_ . But this chromosome is not inactivated as the 50% of the X chromosomes in females. So I'm not sure if it's possible to have a different kind of vision in this case.
--- It's more complicated
Actually you can have more than 1 copy of the color genes in each chromosome, and there are more than two variations of each gene, so it's more complicated.
[+] [-] jacobolus|11 years ago|reply
It would certainly be possible for a genetic mutation to result in an extra mutated copy of the short cone pigment gene, but I don’t think I’ve heard of variants of this gene with slightly different light sensitivity than the usual type (they might exist though?). By contrast “non-standard” version of the medium cone pigment gene is relatively common.
See: http://ghr.nlm.nih.gov/gene/OPN1SW http://ghr.nlm.nih.gov/gene/OPN1MW http://ghr.nlm.nih.gov/gene/OPN1MW2 http://ghr.nlm.nih.gov/gene/OPN1LW
† We should properly refer to the cones as long, medium, and short rather than red, green, and blue, since color is computed from differences in cone responses.
[+] [-] tuzakey|11 years ago|reply
[+] [-] jwatte|11 years ago|reply
[+] [-] tgb|11 years ago|reply
http://en.wikipedia.org/wiki/Imaginary_color
[+] [-] vixin|11 years ago|reply
[+] [-] edcastro|11 years ago|reply
[+] [-] gaius|11 years ago|reply
[+] [-] moneypenny|11 years ago|reply
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[+] [-] Kiro|11 years ago|reply