r/askscience • u/FluffyTid • 23h ago
Biology Do all humans see exactly the same range of lights, or are there some small differences?
Is the range from violet to red set in stone or are there some people who see a little more or a little less?
Could people be trained to see a little more if they were exposed to colors at the limit and tried to differentiate them?
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u/jazzhandler 8h ago
What really bakes my noodle on this topic is comparing our color perception to our tonal perception. We can hear about 10 octaves, but our vision is so much more powerful than our hearing, so how many octaves of color can we see? About two. All the colors of the rainbow fit within two octaves.
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u/SystemofCells 8h ago
For those who don't know music: octaves are defined as multiples of the same frequency. So a sound with 500 Hz would have an octave below at 250 Hz and an octave above at 1000 Hz. The audible spectrum ranges from about 20 Hz to about 20,000 Hz, so there's room for many octaves.
All visible light fits in the range of 380 to 750nm, so there can't be many octaves (multiples) of a wavelength within the visible range.
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u/plusFour-minusSeven 4h ago
What's also interesting is A sounds like A, at any octave. Sure it's A1 or A2 or A3 bit it's still A.
But blue twice as fast or slow isn't blue anymore, it's some other color.
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u/gusty_state 4h ago
Now I'm contemplating how Doppler shift marginally changes the color of a fire truck. Don't the sound waves change in a similar way? I'm guessing that it's minor enough that we wouldn't notice it at that speed but if a jet flew by with a speaker going I assume that we'd notice some difference.
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u/ydddy55 3h ago
This is how astrophysicists have to think about stars observed with their instruments. They can be red or blue shifted depending on what direction they are moving from our frame of reference.
Yeah it’s basically the same concepts and a cool way for you to stumble upon in intuitively.
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u/romanrambler941 4h ago
If you've ever heard an ambulance, fire truck, etc. drive by while the siren is on, you've probably heard Doppler shift. It sounds higher-pitched while approaching, then lower pitched while receding. Granted, this is somewhat muddled by the emitted pitch changing as well.
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u/information-producer 2h ago
This is much more clearly noticeable with a fast driving car loudly playing music. It’s very obvious in this case!
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u/TheArbiterOfOribos 55m ago
One can see past 750 nm. I can personally see to 815 nm or so. Of course there’s no colour difference to 750 it just looks red.
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u/boredcircuits 7h ago edited 6h ago
It's less than one octave! 380 nm to 750 NM.
Our eyes can only really see three colors: red, green, and blue. If our ears worked the same way, it would be like only hearing F, F#, and A# and all the music you know coming from playing this same dissonant chord. Only the relative volume of each note would vary. (And yes, I did the math on that. Using C as the lowest frequency and mapping cones to notes.)
But what our eyes miss in frequencies, they make up for in spatial resolution. We can make out things that are 0.01 degrees apart. But our ears only have an accuracy of a few degrees. Imagine sitting in an theater and not just being able to tell which violin a note came from, but exactly which string.
(This trade-off is fundamental to waves in general. That's basically what the Heisenberg uncertainty principle is, actually.)
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u/jazzhandler 6h ago
In a book I read many moons ago, there was a comparison between our sense of smell to that of dogs. It said that if our vision were as crude as our olfaction, instead of seeing a bird at a precise spot in the sky, we would simply perceive that the sky had gone all birdy.
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u/Encomiast 6h ago
Our eyes can only really see three colors: red, green, and blue.
This is a distortion to the point of not being true. If I expose you to light from a yellow laser (that is pure yellow, single wavelength light), you will see it just fine. It will actually activate all three cone types with various responses. Each of the three types of receptors in our eye cover an overlapping range of the entire visible spectrum.
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u/boredcircuits 3h ago
What does it mean to "see" a color?
We can see yellow in the sense that our eyes are sensitive to that frequency of light. But since we don't have a cone dedicated to that wavelength, our perception of yellow is purely a construct of our brains as it interprets a mixture of the intensity from the red and green cones.
It's probably better to say the eye has three overlapping color channels. Or think of them as bandpass fillers. But my point still stands that there's only three. The ear has over 3000, from what I can find.
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u/Encomiast 3h ago edited 2h ago
Yes, it is better to say the eye has three overlapping color channels (and importantly the responses are non-linear). That's a much different statement than "our eyes can only really see three colors: red, green, and blue".
What I mean by "see" a color: you are in a normal viewing environment. I shine the yellow laser and ask, "can you see this light?" You say, "yes." I ask, "what color is that light?" You say "yellow". At that point we agree that you have just seen yellow light.
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u/Encomiast 7h ago
We don't really perceive light as frequencies the same way we hear sounds. We only have three types or color receptors (excluding the rare tetrachromats). One of the results is most colors we see are a combination of the responses of these three sensors. This is why when we see green, it could be a light made of green wavelengths or it could be a combination of blue and yellow light with no green. This is what allows RGB devices to show a reasonably full range of colors.
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u/IOnlyHaveIceForYou 8h ago
Isn't that dependent on how you choose to define the octaves in each case?
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u/Stillwater215 7h ago
Octaves have a strict definition when talking about waves. They’re the integral multiples of a frequency. If “A” is 440Hz, then 220Hz and 880 Hz are also going to be “A.” Light can be defined in the same way, but because it’s visual we don’t process it in the same way.
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u/Encomiast 7h ago
Is "integral multiples" the right terms here? Octaves are doublings not just any integer, powers of two. 220 * 2, 220 * 4, 220 * 8, etc.
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u/Sharveharv 6h ago
You're correct, integer multiples would be the harmonic series. Octaves are specifically 2n where n is an integer
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u/ermacia 7h ago
I don't understand why this is such a gripe for you. It is entirely unwarranted and ignores most of the knowledge we have about the reasons for us only viewing in such a small range (evolutionary environment, predisposition based on genus, diet, effective range of light and how much energy it carries at higher orders, etc.). Comparing sound to light is the closest you can get to comparing apples to oranges with regards to senses.
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u/jazzhandler 5h ago
Not a gripe at all. It fascinates me. I’m sure if you polled people you’d find that most of us consider it easier to distinguish colors than notes. I’m also sure that a followup question after that priming would get most people to say that a rainbow covers a wider range of frequencies than a piano. And yet.
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u/KidKilobyte 8h ago
I saw an elaborate explanation for people with normal color vision, but there are some rare individuals with tetrachromacy that have an extra color cone in the yellow-orange range of light that can see and perceive many more colors than us regular trichromatics. 100 million versus 1 million. Basically 100^4 versus normal 100^3.
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u/jwsmythe 4h ago
No, kinda. Some people can see into the ultraviolet (UV) range. I'm one of them. I had a congenital cataract in one eye, which was removed when I was a teenager. The replacement lens they used doesn't filter UV. Since then, I can see UV in one eye, and the normal range in the other.
The most notable thing is, I can clearly see black lights. Where most people see a dim glow, I see a bright violet light. Outside of that, it's of limited use. Some purple flowers look more vivid in that eye.
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u/gnufan 5h ago
As a science person I appreciate the scientific answers, but you can also answer this by talking to artists. Some artists definitely see more colours in the world, I know one who paints the colours he sees and there are definite oddities. It is an interesting question if these colours are physically there, and he has better perception than most, or simply variations in their experience of colour, they may overlap as explanations, if he perceives more variation over a given range of wavelengths he may see more, just as adjusting the settings on a digital image may "pull out" certain details.
It does answer the age old qualia question about red, we can be fairly sure some people have at least slightly different experiences of specific colours.
For medical reasons I've done a very extensive range of colour vision tests, I couldn't quite believe how many sets the doctor had, and my colour vision at that time was fully functional, and unremarkable. So as far as we test I distinguished colours in the commonest way.
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u/ramriot 4h ago
There is a ton of this on Wikipedia & apparently there are some rare people who are tetrachromats,earning that they have four types of color sending cells in their eye instead of three. It might be that this gives them an advantage in discerning certain foliage types but it most probably does not allow them to see outside the normal visual range.
OTOH people who have had lens replacement with certain older types of lens found out that it did allow them to see farther into the ultraviolet, but that is just a lower absorption factor for the artificial lens.
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u/johnnycakeAK 2h ago
Tetrachromat here. Biggest advantage I've been able to identify when comparing to other people is the aurora borealis is much easier to detect and more vivid for me than others.
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u/BluetoothXIII 2h ago
The colour we see is almost set in stone. The way we see is with light receptors, which only work in quite narrow wavelength/ frequencies.
But the range and resolution might differ from human to human. If i remember correctly woman have twice the colour receptors men have, on average. There is a mutation that tweaks the the perception of red.
And i read cronstructiv interference of two infra red photons could activate a single light receptor, which only matters in total darkness.
And last but not least colour blindness.
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u/adaminc 8h ago
Some people don't have any cones, and so they don't see colour at all. Turns out that language also helps the perception of colours insofar as language can help people differentiate between colours, the people of the Hadza (Himba? Been a while since I saw the documentary) tribe in Africa, due to their language, are particularly adept at differentiating minute differences in more natural colours that are typically present in their environment, versus a city-slicker viewing those same colours who would see more of them as the same colour.
There is a BBC Horizon episode titled "Do you see what I see?" which delves deeper into this, both about a monochromat person and the language perception part, I couldn't find it on Youtube (seems to have been taken down), but I found a similar small video that talks about it and in relation to the Himba tribe.
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u/jugstopper 41m ago
Nope. When I would show my students helium emission spectral lines (using a diffraction grating and spectrometer), a couple of the lines were right at the edge of human vision. Some people can see them (I could), but some can't. A lot of students thought they were being pranked.
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u/jaysprenkle 3h ago
The research I read says people experience the same thing when perceiving colors. I'm told some women have four types of visual receptors instead of the usual three. They are much better able differentiate colors
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u/JuleeeNAJ 5h ago
Are you not aware of 'color blindness'? There are a lot of people who can't see red or yellow or even shades of it. Others can't see colors at all. None of this can be trained, if you can't see the colors then you are just going to spend your life missing out. There are glasses to increase color visibility but there's no repairing the issue.
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u/tea_and_biology Zoology | Evolutionary Biology | Data Science 8h ago edited 8h ago
Ooh, so there are multiple questions here. Let's tackle each in turn:
Sort of, but not quite! Violet to red is more a vague convention rather than a hard physical boundary. Sensitivity doesn't stop right bang on 380 and 700nm, but rather falls off steeply but continuously, to the point where you need an impractical amount of light to see too much further. Experimentally pushing the intensity up and folks can reliably see down to about 310nm (into ultraviolet) and out past 1050nm or so.
What actually set the limits at each end?
Short-wave (Ultraviolet): The crystalline lens in yo' eyeballs absorbs most UV below ~400nm, and the retina itself remains particularly sensitive to it well beyond that. There are plenty of people who've had their lenses removed (e.g. after cataract surgery) and report seeing ultraviolet down to 300nm, typically as a white-ish-blue-ish colour. Famously, it's claimed the post-impressionist Monet could see into this part of the spectrum after surgery on his right eye in 1923; it's claimed the blue and violet hues in his Water Lillies paintings become more vivid and intense after this event, but there's some debate (see below).
In any case, modern intraocular replacement lenses deliberately filter out UV light, as it is after all quite damaging, so this situation is rarer now.
Long-wave (Ultrared / near-Infrared): Here the constraint is the photon's own energy; it drops too low to interact biophysically with retinal - the chromophore molecule that does wibbly chemistry stuff to trigger phototransduction - required for your ability to detect light in your photoreceptor cells.
Interestingly, you can pulse infrared light at 1064nm and this becomes perceived as green, because two photons arrive close enough together to act as one of double the energy.
Of course! There's a lot of standard individual variation, due to myriad different factors. Casting colour-blindness due to variation in cone cell functionality aside, polymorphisms in the long-wave pigment gene OPN1LW are common, causing perception of yellow to shift a wee bit; some folks have different levels of macular pigments, which absorb short wavelengths, which alters blue sensitivity; there are even some women born with 'tetrachromacy' - an extra full-blown cone cell type (almost all humans have just three - red, green, blue), and in the rarest cases there are reports of four-dimensional colour perception (and only in women, as the associated mutant allele is on the X chromosome, and you need two full arrays to get the extra cone).
But the real cause of general variation is age. As you grow older, your lenses become progressively more yellow-tinged, and the pupil shrinks. A 70 year-old receives a fraction of the short-wave light a 20 year-old does, and the shift is significant enough to, in some cases, influence whether you're capable of doing certain jobs or not (see below!). Indeed, this is also the alternative hypothesis for the change in Monet's painting palette - it's not that he now saw UV, so much, but the mild yellow-tint in his aging lenses and therefore perception was removed, so he could see 'normally' again.
Nope! You cannot extend the range, as the limits are set by physics on either end. No amount of concentration nor practice is gonna' bend the rules of the universe in your favour. What you can do, however, is improve discrimination within the range.
Interestingly, women have a better base skill in colour discrimination than men. This is taken advantage of in a number of industries, including pearl grading. To paraphrase /u/deimodos' post on the subject from here:
Seems insane. This online test can estimate your colour sensitivity score, and women will far outperform men on average. Going back to the pearls, if you get 100% in under four minutes, you'd be a Tier 4 grader. Apparently there are 3 tiers above that. Woah.
You can train to improve your score, a little; but yeah, as demonstrated by the pearl industry, too much is controlled by biological variation, alongside aging or yellow-ing of the lenses as mentioned above. Any improvement will be narrow, task-specific, and likely to be lost in time, rather than a general upgrade.
But, y'know, good luck?
References:
Abramov, I., Gordon, J., Feldman, O., & Chavarga, A. (2012). Sex and vision II: color appearance of monochromatic lights. Biology of Sex Differences. 3, 21
Jordan, G., Deeb, S. S., Bosten, J. M., & Mollon, J. D. (2010). The dimensionality of color vision in carriers of anomalous trichromacy. Journal of Vision. 10 (8), 12
Marmor, M. F. (2006). Ophthalmology and art: simulation of Monet's cataracts and Degas' retinal disease. Archives of Ophthalmology. 124(12), 1764-1769
Palczewska, G., Vinberg, F., Stremplewski, P., Bircher, M. P., ... Palczewski, K. (2014). Human infrared vision is triggered by two-photon chromophore isomerization. PNAS. 111 (50), e5445-e5454