Normally, the human retina contains four types of light-sensitive receptors: three types of cones and one type of rods. The receptor proteins contain the chromo — iodopsin in the sticks, the rhodopsin in the cones. The role of the latter in bright lighting is insignificant, so for a person there are three "basic" colors: blue, red, green — all the shades we perceive are formed by their combinations.

Since each of the yodopsins allows you to differentiate about a hundred shades, a person with normal vision is potentially able to distinguish about a million color combinations. Adding another type of receptor increases this number to one hundred million. Concetta Antico is a carrier of a mutation in the "red" iodopsin gene, whose sensitivity has shifted to the short-wave region. Special features are best displayed when distinguishing reddish-yellowish and purple shades: the color scheme of her paintings focuses on these colors. The additional color pigment also increased color sensitivity in low light, allowing you to distinguish between shades at dusk and in the shade. 

The eyes of the mantis shrimp (Oratosquilla oratoria) have 16 light-sensitive receptors.

My question is: What needs to be changed in the structure of the human eye to be able to see ultraviolet and infrared radiation, as well as to be able to see better in the dark ( That is, to have a good enough night vision). And at the same time distinguish significantly more colors in the visible range ( if you consider that the appearance of the 4 receptor allows you to distinguish 100 times more colors than ordinary people. Then when the same 16 light-sensitive receptors appear, we can distinguish hundreds of millions of colors, or even several billion! )?

Also keep in mind that you need to turn the chromatins in the retina so that the nerve comes out from behind, not in front. This will remove the blind spot to reduce the overall length of the nerve and provide a greater amount of chromatin for each surface area. With appropriate adaptation of the primary processing layer on the back of the eye ball (duplication and offset integration), which can be used to increase the speed of perception by a factor of 2x to 4x, or the details of perception. 

( Human eyes absorb 90% of all photons before they reach the photon receptors. And we need at least 9 photons hitting an individual receptor before it registers a light source, (before it "sees something). This means that by gluing the receptors further forward, we could (optimally) increase the light sensitivity by a factor of ten. )

When making decisions, it is advisable to familiarize yourself with similar questions, where there are several interesting solutions that it is desirable to combine:

Colors of Things Outside the Spectrum

How to modify the human eye to see into the ultraviolet and infrared bands?

Supplement: Please offer solutions related only to biology, so no implants or artificial eyes. Also do not ask questions regarding too much information and the difficulty of processing ( if you know the ways of how you can reduce the difficulty of processing, I will be glad to hear ).

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    $\begingroup$ You just reminded me about imaginary and forbidden colours. Magenta and Stygian blue being examples. Brains are more than capable of processing ridiculous signals being fed to them by our eyes. $\endgroup$
    – Joe Bloggs
    Commented Feb 26, 2020 at 16:48
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    $\begingroup$ That said: how is your question not simply a duplicate of the second question you link? $\endgroup$
    – Joe Bloggs
    Commented Feb 26, 2020 at 16:52
  • $\begingroup$ You could also look into having eyes that perceive the polarization of light. This could allow certain visual feats like seeing through bright glares or seeing through reflective surfaces like glass and water. There are a number of animals that have polarization vision. $\endgroup$
    – David
    Commented Feb 26, 2020 at 17:21
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    $\begingroup$ (1) Humans have very good night vision for a diurnal animal. (2) To see near infrared all that is needed is a suitable phototransduction protein. (3) Seeing near ultraviolet is more complicated, because the eye lens is opaque to ultraviolet. The ordinary visual pigments are sensitive to UV light, so no new pigment is needed; people with their lenses removed can see in near ultraviolet. $\endgroup$
    – AlexP
    Commented Feb 26, 2020 at 17:48
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    $\begingroup$ I know it's not entirely related, but such a thing already exists. Tetrachromacy is an extremely rare condition where the person has an extra type of cone in their eye. This allows for over 100 times more colors to be perceived than your average Trichromatic folk, as you mentioned in the question. $\endgroup$
    – Greenie E.
    Commented Feb 26, 2020 at 23:24

5 Answers 5


Vision in the near UV part of the spectrum is easy: humans can already see it.

The receptors in the human retina can see light of about 300nm, but the lens filters out light below about 400nm. It is thought that the 'blue revolution' in Monet's art lat in life was a result of his cataract surgery, after which he was able to perceive different colours than he was able to before, and most especially, was able to perceive UV light.

A number of post-IOL surgery patients have reported similar effects, namely, that they can see a different kind of purple. Usually, lens implants filter out UV light; but some patients report that they can see this "extra purple" around their peripheral vision -- where the IOL can't physically filter.

This would be the easiest fix, in all likelihood. Change the structure of the lens to allow the already visible UV light into the eye.

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    $\begingroup$ wont this be a double edged sword? if more UV light gets to the eye, the eye will suffer damage from the UVA (maybe even UVB) radiation? $\endgroup$
    – Nullman
    Commented Feb 27, 2020 at 13:24
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    $\begingroup$ @Nullman Maybe. Or the reverse - it's possible the retina heals better than the lens. $\endgroup$
    – Luaan
    Commented Feb 27, 2020 at 13:52

There are two things involved:

  1. ability to sense a larger range of colors - including extended wavelength range and chromatic dimensions. Have to do with the human eyes transparency at different wavelengths and the fact retina is using only three dyes (or less, for the cases of color-blindness)
  2. ability of the brain to combine the sensed signals

Links - apologies, but I'm too tired to organize a coherent answer.

Right. If you don't want to mess with your eyes, get around using sonochromatism - your brain is quite plastic. If it works, go say thanks to Neil Harbisson


The first step is to give a look (pun intended) at the retina of most birds eyes, which have a 4th cone type to see UV. Differently than mammals, their cones have an oil drop to better constrain the wavelengths detected and reduce the overlap with other cone types. Also, birds' cone are much more thin than mammalian ones.

However, birds also have some downsides. Mammals perceive contrast better than birds and birds have a pecten inside their eye blocking part of their view creating large blindspots. Their retina have no blood vessels, so this is the reason why they need the pecten.

Also, humans, like all vertebrates have an inverted retina, which means that blood vessels and nerves are in front of the rods and cones instead of behind them. Cephalopods have non-inverted retinas.

Cats have a tapetum lucidum behind the retina to allow them see better in the darkness, but at the expense of decreasing their visual acuity.

As elemtilas said, people who get a surgey of cataract can see some UV. See here for more about that.

Further, even on mammals, reindeers do sees UV light.

For IR vision, that is more complicated. The reason is that since mammals are warm-blooded, they simply glow in the near IR-range, so any receptive cone would be always saturated and blinded. Animals which are able to see some IR are all cold-blooded, mostly are insects, but some cephalopods, crustaceans, molluscs, fishes, amphibians and some snakes do see IR. But no way birds or mammal can do that. Note that altough snakes see IR, they don't use their eyes for that, instead they use their pit organs, as if those are a distinct set of eyes for detecting IR, but with a very poor visual acuity, resolution and contrast. So, to add IR vision, you would need to somehow shield the eye from the body own glow.

So, I think that you could:

  • Start with a human eye.

  • Replace the mammal cones and rods by avian ones, including adding the avian UV cone. If you are unable to do this, try to at least introduce the reindeer UV cone.

  • Make the nerves and blood vessels connect them from behind the cones and rods, instead of in the front of them. This would also allow those cells to collect more light and be better vascularized. Then they could also be cramped more tighter, yielding a sharpen image. Since the much better vascularization also gives those cells more nutrients and oxygen, I think (not sure though) that they would then be able to yield a better contrast and get rid of the need of having either pectens or blindspots.

  • Make a special tapetum lucidum in the eye that can progressively change from reflective in darkness to opaque black under direct sunlight to make better adaptation for different light conditions beyond what the iris is capable.

  • Change the IOL in the eye for something that is also transparent in UV, maybe you can get an inspiration from reindeers to keep it compatible with being mammal.

  • You end up with three layers at the retina. The internal one features rods and cones. The other two are (a) the blood vesses, nerve endings and retinal ganglion cells and (b) the tapetum lucidum. Not sure which one would work best as being the middle layer.

Adding a UV cone might have a few downsides. Notably, if you add a new type of cone in the retina, you will need to spread the existing ones a bit to make room for the new ones, which might reduce visual acuity. Also, human eyes focus images with the red and green cones while the blue ones suffer from chromatic aberration and due to them being far less numerous, poor visual acuity in the blue. However, it shouldn't be very hard to balance this, specially if you use avian cones which are much thiner than mammalian ones. Also, the human brain already does a pretty good job "photoshopping" the image from retina to compensate for a lot of the vision shortcomings.

Then when the same 16 light-sensitive receptors appear, we can distinguish hundreds of millions of colors, or even several billion!

Unlikely to work as you think. It is probable that seeing so many colors would require the correspondent neuron wiring in the brain. So, altough some animals have a large number of photo-receptors, this could be at the expense of being unable to properly blend all those color or having trouble to discern different similar shades of the same color or something else. Also, user MJ713 points out in a comment that research on mantis shrimps shows that they are actually fairly bad at distinguishing between similar colors.

About tetrachromacy, I will cite this:

However, the most stringent test of our hypothesis was between the female trichromatic subjects and the female four-photopigment heterozygote subjects. As shown in rows 1 and 2 of Table 2, the mean numbers of bands delineated by the two groups of females (7.6 vs. 10) were significantly different ( p < .01). This comparison eliminated differences in performance attributable to gender and thus was a stronger test of our hypothesis that having four pigments yields a perceptual difference.

At present, four-photopigment female individuals are reported to be rather common, by some estimates occurring in up to 50% of the female population (M. Neitz, Kraft, & J. Neitz, 1998). It is also the case that an estimated 8% of males presumed to be color “normal” likely represent a four-photopigment retinal phenotype (expressing multiple L-pigment opsin gene variants that could significantly contribute to color vision; Sjoberg, M. Neitz, Balding, & J. Neitz, 1998).

I.E. There could be more tetrachromats around us that we might be aware. Even most of the tetrachromats themselves must be unaware.

Also, excelent to read:

Also, some years ago, I seen a paper where someone made an experiment with many women and found out some tetrachromats and even identified two different types of tetrachromats with functional tetrachromacity. If my memory don't betray me, one of those groups had an orange as the 4th primary colour and the other had a greenish-yellow as the 4th primary color. However, it was some years ago and googleing for it I was unable to find it again. This basically happens because the red and the green cones are encoded by two genes called OPN1LW and OPN1MW (ha, could find their names with Google at least), which are neighbours in the X chromosome (but absent in the Y chromosome), so during crossover (for women only), a gene that is a mix of half-OPN1LW and half-OPN1MW might end being produced, and there is more than one way to mix them.

Also, in the same occasion some years ago, I also seen a very good webpage which described in profound details, but still in a clean and easily understandable language, all the nuances of how the color vision evolved and how it worked out in the retina, in the retinal ganglion cells and in the brain. However, once again, Google betrayed me.

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    $\begingroup$ "Unlikely to work as you think. It is probable that seeing so many colors would require the correspondent neuron wiring in the brain." - indeed, research on mantis shrimps shows that they are actually fairly bad at distinguishing between similar colors. This strongly suggests that their brains do not "mix" inputs from different cones in the same way our brains do. $\endgroup$
    – MJ713
    Commented Feb 27, 2020 at 6:09
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    $\begingroup$ So you need to create two or three additional light-sensitive receptors ? ( red " iodopsin, is responsible for sensitivity in korotkovolnovoi region. Orange and greenish-yellow ) $\endgroup$
    – user71408
    Commented Feb 27, 2020 at 10:33
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    $\begingroup$ Don't forget birds also just have more types of cones in the eye. 4 instead of the human 3. $\endgroup$
    – John
    Commented Feb 27, 2020 at 10:40
  • $\begingroup$ @FrenchThompson Yes, basically add a new UV cone type, which already exists on other animals and fix up the IOL issue and you probably gets UV vision. The same could be done with IR, if you can somehow shield the eye from the body own IR glow. Check out the edits I did to this answer. $\endgroup$ Commented Feb 27, 2020 at 14:21
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    $\begingroup$ The female tetrachromats have one gene for normal receptors and one that causes red-green color blindness in women who have two such genes, and men (who only get one copy, as the Y chromosome does not have either gene). $\endgroup$ Commented Feb 27, 2020 at 19:29

Check out tetrachromats if you'd like to know about people (specifically, women) who can see more colours in the existing visible waveband - their vision is to ours as ours is to red-green colourblind people, thanks to having a fourth type of colour receptor.

UV and near IR vision may not be that helpful. Seeing in seriously low level light requires enhancements that no biological creature has - instead evolution equips night hunters with echo-location, scent, vibration sensitivity or good hearing (as in owls) instead.

In practice you might be bettor off with better post-processing than better eyes, eg the ability to do the equivaltn of combining a large number of frames of video to get a best image. This can greatly enhance both daytime long-range and night imaging.


I'm not sure on the color issue other than human eyes are actually capable of seeing more shades of color than a computer screen can render (using a RGB scale)... meaning that their are colors you can only experience in real life. Not on a screen or on photos.

As for night vision, many animals (cats come to mind) are more photosensitive than human eyes, both by having more receptors and by being more dilated (reducing the absorbed photons before they reach the receptors). If you've ever gone to an eye doctor, you've probably had your eyes dialated so he can look at them... and then suffered as the sun is ridiculously and painfully bright for the rest of the day. It's almost like being a vampire.

Most night vision for humans is done by goggles that have a small computer in them that will take in photons from the lenses and render them on a screen for for normal human photo-sensitivity (that Night vision green, mostly done because the simplest monitors for these are gonna do green screens). You should not use these anywhere near a light source as it can blind you if the sources is something a naked eye can see just fine with. The US military also has special gun sights that are invisible to the naked eye but when you wear night vision, you can see them on the target (I assume other modern militaries have them, but it's only been described to me by US Military people... they all seem impressed that they can light up the bad guy "like a Christmas tree" and he's totally oblivious to just how much laser sights are on him.

Gear for Infrared and Ultraviolet (and every other part of the non-visible light spectrum... which is to say, most of it) are similarly rendered into visible colors humans can understand. An Infrared will paint a source from violot (low) to red (high) and white (highest) based on the intesity of the infrared light because those are colors we can see, not because Infrared lets you see "more redder red". If you could see infrared, it would probably look like a totally new color you've never seen before (and because we rarely consider it in decrative color, almost all the colors would change based on their reflection of IR light. It's probably best to not describe the color or IR or UV because color is a qualia adjective. You cannot describe color without providing an example of that color. Though you could have fun with this as the person with enahnced color range could be disgusted with the ugly color combo of the fashonista (who is insulted that her perfectly matched outfit looks garrish to his eyes) or handle it like th Kaminoans in Clone Wars (the set was designed with a sterile white look, but this was explained as the Race seeing UV spectrum colors. While we find the whole appearance white and boring, the Kaminoans are stated to actually have some really amazing artwork all over the place that humans cannot see (most of this was in supplemental material and set designer notes If you squint you can see some vague outlines of intricate etched designs).

  • $\begingroup$ UV scopes in Strykers are B&W. Some materials are clear for UV light. $\endgroup$ Commented Feb 26, 2020 at 17:32
  • $\begingroup$ "You cannot describe color without providing an example of that color." Of course I can! But it will be you who won't be able to see it; because you are using only three organic dyes in your retina and your brain didn't learn how to handle more. But, you see?, if only you were to use more than 3... But maybe your brain is already prepared. Give it a try, see if you are among the few that can perceive yellowish-blue or redish-green youtu.be/cQCsDfEqr9o?t=518 $\endgroup$ Commented Feb 26, 2020 at 17:41

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