PetaPixel

A Retinal Neuroscientist’s Rebuttal: Why Humans Can’t See Near Infrared, No Matter What They Eat

ir_1

One of the more interesting stories we ran across this weekend was an initial update from a small group of scientists who claim to have successfully extended human vision into near infrared. Their data seems to show that they have, indeed, managed to do this simply by altering their subjects’ diet by restricting vitamin A1 and supplementing with A2 in order to create a certain protein complex. You can read more about this here.

The results seem exciting, mind-blowing even. But retinal neuroscientist and photographer Bryan Jones begs to differ, and he has been kind enough to let us reprint his full rebuttal below.

The TL;DR version is that, no matter what we eat, don’t eat or supplement, the four kinds of photoreceptors in our eyes simply cannot pick up any wavelengths of light beyond 650nm at the upper limit. According to Dr. Jones, it is a physical limit that cannot be shifted.

Image credits: Eye iris by Petr Novák, Wikipedia

Image credits: Eye iris by Petr Novák, Wikipedia

Here is the Still Long; But Worth Reading (SL;BWR) version from Dr. Jones himself:


Preface

Hypothesis driven study is a cornerstone of science. It is not the only way to do science, but it is one of the most powerful. Hypothesis driven science can also be misused to great damage. How one properly performs hypothesis driven science is through the formation of a hypothesis, an idea that represents how you think something might work. The scientist then endeavors to *disprove* that hypothesis through any and all means available. When you fail to disprove your hypothesis, you have to consider it might be true. The dangerous, and incorrect way to perform hypothesis driven science is to form a hypothesis and then proceed to attempt to collect data to *prove what you want to believe*. This approach has resulted in not only bad science, but it has even brought countries to war.

The process of performing science is a contract with society. A contract that obligates scientists to not only carefully perform their work, but also to communicate that work to society. As part of this agreement, we endeavor to correct misinformed or constructed or communicated science through the peer review process. When the peer review process is circumvented and the science is presented to the wider community or popular press without peer review, the error checking component of science is weakened and society can suffer.

My intention in critiquing this effort publicly was not to prevent people from engaging in science. On the contrary, these days with plummeting science funding, we need all the enthusiasm, support and excitement for science we can get. I am a firm believer in science and public science, but the authors of that study have not done their homework and they are releasing incremental, unconfirmed data (that is biophysically impossible) to the general public. I don’t think their goals or motivations were selfish or nefarious, but it has the potential and apparently did mislead many people who do not know that particular area of vision science. That had to be corrected.

rodsandcones2

Photoreceptors vs. Infrared detectors

I am a photographer and read PetaPixel quite regularly. I am also a visual neuroscientist who knows a little something about how the visual system works from the molecular to the behavioral side of things and I had to take exception to that article claiming to have successfully extended human vision into the infrared.

I am including my text explaining why, here:

In order to understand why humans seeing in the IR range will not work, you just have to have a basic understanding for how photoreceptors work. This is not hard and there are a number of resources available online that explain it rather nicely. For instance, there is an excellent summary here on Webvision, the Internet’s very first online textbook:

In short, there are 4 kinds of photoreceptors in our eyes, rod photoreceptors which detect electromagnetic spectral energy from ~400nm to ~580nm with maximal sensitivity at 496nm (blue/green light), and long, middle and short wave cone photoreceptors. Three different cone mechanisms can be detected in behavioral, psychophysical, physiological and molecular staining in non-human primate and human retinas. This 3-cone mechanism is what gives humans trichromatic vision, which most humans have. A percentage of humans are color blind and are thus dichromatic. Click here to see how dichromats see the world. The long wavelength sensitive L-cones (“red cones”) are known to be maximally sensitive to wavelengths peaking around ~560nm, medium wavelength sensitive M-cones (“green cones”) peak around ~530nm, and short wavelength S-cones (“blue cones”) peak at ~420nm respectively.

Rod photoreceptors are most sensitive at low light levels (luminance below moon light) and cones are sensitive to brighter light. When light levels reach their upper limits of brightness detection (moon light), they start to shut off and cones pathways take over from rod pathways. This is why colors seem washed out at and below moon light levels and become more detectable at brighter light levels.

rodsandcones1

Importantly, the absolute limit of long wavelength photoreceptors in humans is less than 650nm at the very end of the response curve. Infrared light in the electromagnetic spectrum starts at the absolute limit of around 700nm and goes to 1mm in wavelength. There is no overlap with any infrared electromagnetic energy with any photoreceptors that humans have. These limits in human photoreceptors are based upon molecular structures of photopigments. These photopigments can be “tuned” within a narrow window within the red/blue/green spectrum, but getting them to be sensitive to infrared wavelengths is impossible within the limits of physics or biophysics.

When pigments in photoreceptors (opsins and chromophores derived from vitamin A) capture a photon, they change their shape which induces a Rube Goldberg like series of enzymatic cascade reactions called phototransdution that alters the electrical current in photoreceptors, which changes how they signal the next set of neurons in the retina (there are over 70 types of neurons in the mammalian retina). These neurons are assembled in circuits then process a variety of types of information including brightness, contrast, primitive movement and luminance, among others, before passing that information on to other areas of brain for further processing.

Now, biological systems can detect infrared energy and there *are* species that can detect infrared wavelengths. Notably snakes like vipers, pythons and boas have pit organs on their faces containing a specialized organ or membrane that does detect infrared radiation up to 1 meter away from them.

boa_1

However, there are no photons that are involved in the infrared detection and the pit organs are not wired up to the snakes visual system. Rather, the pit organs are connected to the somatosensory system, the part of the nervous system that detects temperature, pressure, pain and touch. These pit organs are true infrared detectors that function with a completely different molecular mechanism for detecting electromagnetic energy by utilizing another set of ion channels called TRPA1 receptors that detect heat instead of light.

Interestingly, these receptors also are sensitive to irritants like mustard and wasabi, but whether or not wasabi is attractive or repellant to snakes, I don’t know. TRPA1 channels activate/open when certain temperatures are reached (higher than 28 °C) that allow ions to flow into the neurons they are embedded in and triggering an electro-chemical signal kind of like the photoreceptors. Their differential positioning around the head of the snake allows them to orient to where the heat/prey might be, but it is not vision.

So, while there is biology that can detect infrared energy, there is no way, shape or form that a photoreceptor in a human can take, regardless of what you eat in your diet that will allow you to “see” infrared energy with your eyes. You can “feel” infrared energy through your skin and detect warmth and cold, but those parts of the electromagnetic spectrum are simply unavailable to visual systems.


There you have it, a ‘lay-person friendly explanation’ as to why Dr. Jones doesn’t believe there is ever going to be a “near infrared vision supplement/diet” in our future.

We put Dr. Jones in touch with the creators of the original experiment and they are currently emailing back and forth. If any significant updates arise out of that conversation, we will be sure to update this post.


Image credits: Unless otherwise indicated, all photographs courtesy of Dr. Bryan Jones.


 
  • Sir Stewart Wallace

    Damn, and I was just about to start over-dosing on Vitamin A2. :/

  • DLCade

    Science saves another life…

  • glims

    Funny, he talks about infrared, but our project has to do with near infra-red. I’d look forward to you posting the rest of that conversation. We haven’t heard anything from him since we called him on being utterly dismissive and not reading the background information before sending out that wall of text…

  • Banan Tarr

    NIR is one part of the entire spectrum of electromagnetism known as infrared (so when he talks about infrared that includes NIR). I noticed you didn’t respond to one of your comments on your project about potential visible light leaking through your IR filter/equipment… Are you guys also reading other wavelengths (i.e. visible light) at the same time, to isolate and ensure no leaking is occurring?

  • glims

    Talking about infrared and referencing heat is obviously not inclusive of NIR. NIR is around 750-1400nm while the long wave infra red is way over at 8000-15000nm. The distance between the two of those is 21 times more broad than the amount of the spectrum that we can see…

    Sorry about not answering that question where you saw it. We have replied to so many comments (especially on reddit) that we kind of lose track of the duplicates or triplicates…
    We took control readings before the supplementation started and we are normalizing our data against that. Also, we have a control subject with the same setup but taking A1 instead.

    So yes, we are making sure that the readings that we have been getting lately post supplementation are unlike the readings we are getting after supplementation. We really do have multiple controls set up to make sure we aren’t just making it up.

    We really hope everyone will realize that this is _initial_data_ put forth on a blog, not a solid data set, not a peer reviewed paper yet. Initial success meant we got some data. That is all. We hope everyone stops getting so sucked into sensationalist headlines and reads the background materials. It’s a work in progress.

  • OtterMatt

    What background info? Human vision doesn’t extend into even NIR ranges. I gave a modicum of credence to the hobbyist scientifics who did the “study” (it was really a proof of concept more than anything, and they still misread the data), I think I’ll believe the neuroscientist over you, buddy.

  • OtterMatt

    Shame, but he’s absolutely right. Leaking study results to the media before they’ve been verified is negligent at best.

  • glims

    Yes. We know that. That is what we are trying to adjust. Also, the study isn’t over yet, yes, it is a proof of concept, i’m unsure how you can say we misread the data without looking at the whole set yourself, and we’re not hobby scientists, we are both published. Calling someone a hobby scientist without doing your research is really rude.

  • Banan Tarr

    Fair enough – PetaPixel isn’t doing you guys any favors with unqualified statements like: “And they just got their first positive results, successfully extending human vision to 950nm!”

    Perhaps a more carefully worded version: “And they just got their first positive results, successfully stimulating the vision of one human test subject to 950nm!”

  • Carl Pham

    A good illustration of why a little knowledge is a dangerous thing. The good doctor should brush up on his basic physical chemistry. It’s certainly true that retinal does it’s little isomeric flip in response to optical photons, and it’s hard to see how that mechanism could be activated by IR photons, quantum transitions being as on/off as they are. But IR photons are routinely absorbed by molecules, and they do provoke transitions in the vibrational modes, and while it is very unlikely, it is not impossible that certain near IR photons could provoke some odd vibrational changes in the molecules that leads, more or less accidentally, to the experience of vision. We already know that “vision” can be provoked by things other than actual light — just push your fingers on your closed eyeballs and look at the pretty stars. That’s not absorption of photons going on there, but the system is being triggered nevertheless.

    As a scientist myself, I would take issue with this sniffing at crowd-driven science. This is the best kind, in part because it’s not hamstrung by ideas of what is, and is not, possible. It’s purely fiddling empirical driven. Do the experiment. Find out!

    He’s quite correct that after you have done the experiment, you must be exceedingly cautious about what you claim it represents. You can say we’ve done experiments which suggest the possibility of near IR vision but you can’t say aha! we’ve proven it! More importantly, you should be willing to address criticism from people who are skeptical, and provide them with every bit of your data and methods, so they can attempt to reproduce it themselves, or, more likely, do additional experiments that show your hypothesis is wrong. This is, for example, what the CERN people who thought they detected faster-than-light travel did. They didn’t just toss the data because we all know relativity says that’s impossible (which I’m guessing is what Dr. Jones would have — wrongly — suggested they do.) They published it and invited others to criticize, and endured both the intial storm of publicity Einstein might’ve been wrong, boffins say!!! and the humbling ultimate result of being proved wrong. That’s science. Not any veneration of Accepted Theory merely because it’s accepted.

  • Realsciencejim

    Can I call you a dumb cee you next Tuesday then? Your science is flawed, your study is wrong, and your attitude leaves something to be desired.

  • OtterMatt

    Real science is 90% about being proven wrong, and generally being pleased with that. 10% or less is about actual discovery.

  • http://prometheus.med.utah.edu/~bwjones/ BWJones

    You did not read what I wrote… The biophysical limitations of the long-wavelength cone is absolutely at its limit at ~650nm. Shifting that biophysical performance >50nm is simply not within the boundaries of possibility. And the curves you *DID SHOW*, indicated responses at 850nm and 950nm… Beyond credulity.

  • glims

    Sure buddy. You can also read our official rebuttal later that we will be posting later this evening.

  • mesocyclone

    A bit off topic, but the following seems odd: “. Notably snakes like vipers, pythons and boas have pit organs on their
    faces containing a specialized organ or membrane that does detect
    infrared radiation up to 1 meter away from them.”

    Why the 1 meter distance? IR radiation doesn’t have a distance limit. Presumably one of these critters could see an IR bright object at 10 meters, or 100 meters or whatever.

  • glims

    Yes, we have. And we will be posting a full official response to your rebuttal a little later today. Our lead eye guy was really excited to write it.

  • whisky

    petapixel … great to save face, but how about less fluff, more facts?
    how about coloring all your unverified posts (re-posts) in pink … or something?

  • http://prometheus.med.utah.edu/~bwjones/ BWJones

    Hey Carl,
    Why don’t you do some calculations on how much energy would be required to activate those bonds from IR energy sources… Go ahead, I’ll wait. Never mind, I’ll tell you that in essence, yeah, you can do it, but the heat energy being absorbed would start cooking the tissue.

    Also, that thing where you see stars when pushing on your eyeball? Yeah, those are TRP channels. Completely different mechanism. You can also hit yourself in the back of the head and see stars. Neither one of those are vision nor are they visual processing.

  • http://prometheus.med.utah.edu/~bwjones/ BWJones

    I’ll look forward to reading it.

  • glims

    Just as a heads up, you do know that a lot of what you wrote was copy and pasted from someone else’s writing, correct?

  • Michael Andrew Broughton

    “Importantly, the absolute limit of long wavelength photoreceptors in humans is less than 650nm at the very end of the response curve. Infrared light in the electromagnetic spectrum starts at the absolute limit of around 700nm and goes to 1mm in wavelength. There is no overlap with any infrared electromagnetic energy with any photoreceptors that humans have. ” this is demonstrably untrue. sensitivity drops off sharply, but i’ve personally seen past 750nm while working with lasers. also, i don’t like how this guy tries to conflate near ir and far ir.

  • BillR

    I was looking at my front yard yesterday at a wavelength of 815-885nm through a bandpass filter. I haven’t augmented my diet yet, but why not. Near IR human vision has been known and measured for over a century. The authors’ lack of familiarity with some of this information might be excused, as it was published before they were born. A good and thorough introduction to the subject is referenced below.

    Bill Rudersdorf, Houston

    — — —

    The Sensitivity of the Human Eye to Infra-Red Radiation
    Donald R. griffin, Ruth Hubbard, and George Wald

    JOSA, Vol. 37, Issue 7, pp. 546-553 (1947)

    Partial abstract:

    The spectral sensitivity of human vision has been measured in the near infra-red, in two areas of the dark adapted eye: the central fovea (cones) to 1000 mµ, and a peripheral area, in which the responses are primarily caused by rods, to 1050 mµ. In both cases the estimates of spectral sensitivity are based upon determinations of the visual thresholds for radiation passing through a series of infra-red filters. By successive approximation, sensitivity functions were chosen which were consistent with the observed thresholds.

    The spectral sensitivity of the fovea determined in this way is consistent with previous measurements of Goodeve on the unfixated eye. At wave-lengths beyond 800 mµ the periphery becomes appreciably more sensitive than the fovea. This tendency increases at longer wave-lengths, so that at the longest wave-lengths studied, the radiation appeared colorless at the threshold and stimulated only rods.

  • glims
  • http://prometheus.med.utah.edu/~bwjones/ BWJones

    Where are you claiming that this is copy and pasted from whose writing? Are you accusing me of plagiarism? Is that where this is going?

    Furthermore, you are aware that I am an editor for Webvision, right?

  • iowapipe

    not particularly taking sides: but if you are gonna take a shot at someone, be sure it doesn’t end up as a pot-shot. With him being the author of the work he cited…

  • glims

    Not aware that you are an editor for Webvision. However, I believe that Helga Kolb’s name is on the material that you borrowed from. Some of it is a direct copy.

  • glims

    He isn’t the author. He’s an editor. Wald is the author.

  • http://prometheus.med.utah.edu/~bwjones/ BWJones

    Show me please. Show me what is directly copied as opposed to summarized.

    Also note that I work with Helga Kolb closely on Webvision.

  • http://prometheus.med.utah.edu/~bwjones/ BWJones

    Wald is not the author. Helga Kolb was the author of that article and nothing was plagiarized. Be careful… You are rapidly losing credibility here.

  • glims

    crap, sorry, i said Kobe in a previous comment, many things going on right now.

  • glims

    If you read our response, the second part of that italicized piece, a quote form your rebuttal… if you just drop that into Google… Kolb’s work is the first thing that pops up, with almost every word a perfect match. It’s not even a freshman level of copypasta.

    That’s great you guys work together. Sorry you’re all agitated. Try reading our response and come back with something other than ctrl+v and panic.

  • http://prometheus.med.utah.edu/~bwjones/ BWJones

    Oh, you have got to be #@$&ing kidding me… Seriously?

    You are referring to this paragraph: “The long wavelength sensitive, L-cones (“red cones”) are known to be maximally sensitive to wavelengths peaking around ~560nm, medium wavelength sensitive, M-cones (“green cones”) peak around ~530nm and short wavelength cones, S-cones (“blue cones”) peak at ~420nm respectively.”

    That is paraphrased from the Webvision chapter that I edit and is cited there are deriving from (Bowmaker and Dartnell, 1980; Bowmaker et al., 1980). Its hard to accuse me of plagiarism when I cite Webvision as a source for the material in the previous paragraph.

  • glims

    Sorry, man. Citations are solid, but that’s an entire paragraph, not rephrased. You aren’t paraphrasing it, you copy and pasted it, without quotes. I figure that there are more, we just don’t care enough to dig through it and list them all out. Focus on the work, not the writing errors. How are the scientific points?

    EDIT: We ran the rebuttal through a plagiarism checker. Sorry. Don’t argue with me. I figure someone else somewhere is more upset about this.

  • http://prometheus.med.utah.edu/~bwjones/ BWJones

    I think we are done here. This is the most unprofessional exchange I’ve had since getting trolled on Slashdot. Please post the results of your plagiarism checker here for the record.

    This is *precisely* what I wrote: “For instance, there is an excellent summary here on Webvision, the Internet’s very first online textbook:
    In short, there are 4 kinds of photoreceptors in our eyes, rod photoreceptors which detect electromagnetic spectral energy from ~400nm to ~580nm with maximal sensitivity at 496nm (blue/green light), and long, middle and short wave cone photoreceptors.”

    That is clearly an attribution of record, not plagiarism.

  • glims

    So, no responses about the excellent write up addressing your points?
    And no… what are they called… quotation marks on the attribution of record?

    I’m happy this isn’t a professional exchange. You have done an excellent job of showing what professionalism is. Not reading sources, poor attribution, false claims, outdated data. Complete refusal to address the points put forth that threaten your position. Keep your professionalism, we’ll do the research. You keep the tenure. We’ll live the science.

  • Jeffrey Tibbetts

    It’s interesting that this hasn’t been replied to at all which is really more important than anything regarding plagiarism. I’m still trying to figure out where the 650 upper limit number came from. That’s the ringer. If all he has is the 650nm on that one graph without axis or citation then I don’t understand how the rest matters. Did he get the 650 from the Kolb paper alone or are their studies to back this up?

  • BillR

    Carl,
    Read the literature. As is, the human eye is good to 1000nm or so. Greatly diminished paso 800. I do it all the time. Noticed this almost fifty years ago. Look this reference up before further bloviatiating:

    The Sensitivity of the Human Eye to Infra-Red Radiation
    Donald R. griffin, Ruth Hubbard, and George Wald

    JOSA, Vol. 37, Issue 7, pp. 546-553 (1947)

    Partial abstract:

    The spectral sensitivity of human vision has been measured in the near infra-red, in two areas of the dark adapted eye: the central fovea (cones) to 1000 mµ, and a peripheral area, in which the responses are primarily caused by rods, to 1050 mµ. In both cases the estimates of spectral sensitivity are based upon determinations of the visual thresholds for radiation passing through a series of infra-red filters. By successive approximation, sensitivity functions were chosen which were consistent with the observed thresholds.

  • BillR

    OtterMatt,
    Some “background info” for you. I noticed the sensitivity of my own eyes to NIR, and as a “hobbyist scientist” determined their sensitivity with a series of carefully designed experiments. Later research showed my data agreed quite well with results published twenty-five years earlier. One reference:

    The Sensitivity of the Human Eye to Infra-Red Radiation
    Donald R. griffin, Ruth Hubbard, and George Wald

    JOSA, Vol. 37, Issue 7, pp. 546-553 (1947)

    Partial abstract:

    The spectral sensitivity of human vision has been measured in the near infra-red, in two areas of the dark adapted eye: the central fovea (cones) to 1000 mµ, and a peripheral area, in which the responses are primarily caused by rods, to 1050 mµ. In both cases the estimates of spectral sensitivity are based upon determinations of the visual thresholds for radiation passing through a series of infra-red filters. By successive approximation, sensitivity functions were chosen which were consistent with the observed thresholds.

  • BillR

    A Journal of the Optical Society of America article from 1947 might be of interest, or it just might be beyond your credulity, hard to tell from your attitude:

    The Sensitivity of the Human Eye to Infra-Red Radiation
    Donald R. griffin, Ruth Hubbard, and George Wald

    JOSA, Vol. 37, Issue 7, pp. 546-553 (1947)

    Partial abstract:

    The spectral sensitivity of human vision has been measured in the near infra-red, in two areas of the dark adapted eye: the central fovea (cones) to 1000 mµ, and a peripheral area, in which the responses are primarily caused by rods, to 1050 mµ. In both cases the estimates of spectral sensitivity are based upon determinations of the visual thresholds for radiation passing through a series of infra-red filters. By successive approximation, sensitivity functions were chosen which were consistent with the observed thresholds.

  • http://prometheus.med.utah.edu/~bwjones/ BWJones

    Hey Bill,

    Thanks for that article. The answer is a little complicated, but bear with me. Yes, the early studies did push stimulation down to the near infra-red and you can get responses.

    But here is the deal… You can get any molecule to excite and induce resonance. The problem is that it is not biological and it causes damage. In the UV spectrum, those energies cause vibrational energy to chemical bonds and break them. In the IR range, you cook proteins.

    So, after 1947 when optics and light energy started becoming more of an interest (lasers, etc…), it was found that IR and near IR radiation is dangerous to ocular tissues. Most of the studies performed have been looking at mid and far IR, but its been found that the cornea absorbs most of the wavelengths above and beyond 1400nm to around 3000nm. The real problem with the IR-A or near infrared is the lens which absorbs IR energy from around 900nm to 1400nm. When this happens, you get cataracts. Bad ones. This has been known since at least the 1700s when people started using telescopes to look at the sun or when glassblowers in Italy started developing cataracts.

    Below around 1400nm, that energy is absorbed by the retina. That means heating of the retina and heating of structures that are already operating on the edge of oxidative damage. The interface between the photoreceptors and the retinal pigment epithelium is the area of your body with the highest oxygen turn over per unit volume and its running on the ragged edge of its ability to detoxify and deal with oxidative damage.

    So, if the cornea allows (its bandpass function) most of the IR radiation between 700nm and 1400nm, that radiation is passed directly to the aqueous humor and the retina. Once it reaches the retina, most of that energy is absorbed by the RPE or retinal pigment epithelia. The neural retina then is heated through conduction. The scary thing is that heating can happen in literally fractions of seconds. I did some consulting for the US military a few years ago where we discussed heating with respect to the proliferation of laser weapons on the battlefield and this is a big deal, particularly as many of the lasers and emitters are in the IR range covering near to mid IR. As I recall, the IR studies done on primates by the US Army revealed exposures from 700-1400nm took around 15 minutes to cause obvious burns which is why most optical coherence tomography devices have absolute limits on how long exams can take. However, those studies were gross clinical studies with no protein expression, metabolic or even histology that occurred, so we don’t really know yet what the exposure time is for damage to visual function. Psychophysics studies were not performed on those animals to my knowledge.

  • D.G. Brown

    I’m just a software engineer who pretends to be a photographer, but I think the answer to your question is in the question. Snakes aren’t looking for bright objects. They’re using the organs to detect the FIR from the body heat of prey. Considering the climates that snakes tend to be in, this might not be a huge difference. Additionally, there is the fall off from both the inverse-square law and absorption by the air itself.

    Also keep in mind that the mechanics of the organ are nothing like our eyes. If someone shines a flashlight from a mile away in pitch black, we might be able to see it. However, that’s because our eyes have a high resolution (especially in the center) and our brains are built with serious horsepower for pattern recognition.

    This organ has no resolution (think of it more like an ear that listens for a specific wavelength). It’s like averaging all the light an eye might see into one value. This means that as a light source moves further away, not only is it getting dimmer from the factors mentioned above, it’s getting smaller (which I believe is also squared as size decreases in two dimensions), and therefore, if you think of the whole thing as an average, makes it even dimmer.

    That’s mostly just a guess, though. And it is 4am, so my brain is not entirely reliable ;-)

  • OtterMatt

    Except for, you know, the fact that that would indicated not simply an extension of the abilities of the human eye, but a full-on sprain. If your data contradicts well-known limits of human facility, then your data is WRONG. And that goes double when your study isn’t even yet peer reviewed. You guys stand awfully strong for a study with no more credit than a biochemistry undergrad’s senior design project.

  • OtterMatt

    We’re not talking about 780nm. Not even 785 or so. These guys are saying over 1000nm is feasible. I can’t stop giggling, myself.

  • BillR

    Your comments about NIR damage from high levels of energy are certainly valid, but not the subject of the question as I understand it. For example when outdoors, your retina is receiving about 50% of its energy input from NIR, up to about 1100, where water vapor absorption in the atmosphere (and liquid water in the aqueous and vitreous humors of the eye) mostly attenuate it. It is obviously not dangerous (no, don’t look at the sun!). Longpass NIR filters can allow this fraction of our vision to be seen, with the expected effects of green leafy plants being very light, and “visually opaque” dyes (such as hair dyes) being rendered transparent at these NIR wavelengths. All the talk about lasers and high energy levels is true, but off subject. There is measurable and visible sensitivity in the human eye above 700nm. It has been noted and published for over 100 years. It is codified in the CIE data published in 1931 and 1964, as well as DIN EN 410:2011. Whether this can be enhanced has yet to be seen, but should be easy to test.

  • BillR

    Sir,
    Your hostile attitude will not advance this inquiry. The sensitivity of the human eye well past 700 nm into the NIR is well and long established. It is shown in the CIE standards, both 1931 and 1964, as well as DIN EN 410:2011, among others. It can be demonstrated easily. NIR is approximately 50% of the energy received in normal sunlight, as attenuated by the atmosphere, especially water vapor above 1100 nm. It contributes only a very small part of our visual image, and to be made dominant, the greater part of light below 680 nm must be removed. I ask anyone interested in this to check out the available literature, some of it dating back over a hundred years (the Astrophysical Journal). And I ask that correspondents maintain the dignity of polite conversation on this.
    Bill Rudersdorf

  • BillR

    Jeffrey,
    The sensitivity of the human eye to NIR has been documented for over a hundred years. The CIE 1931 and 1964 tables, as well as DIN EN 410:2011 show this as established scientific / industrial standards. Routinely you see inaccurate “limits” published. The vituperation with which this is being handled by a disorganized and ill tempered writer is no contribution to the subject. Study the literature, there’s nothing odd about NIR sensitivity. It might not be physiologically important, but it exists and can be easily demonstrated. The comments about pit viper IR sensitivity (3-10 micron mostly) not being integrated into vision is contraindicated by research more than 10 years old. In such reptiles, [This IR sensitivity is due to an entirely different mechanism than visual opsins, more if you’re interested!] This IR information is synthesized by the same areas of the brain as is data from the eyes.
    The author of this is not representing the field well.
    Bill Rudersdorf

  • noisejammer

    Per definition, infrared cannot actually be seen with the human eye. I suppose it’s arguably disingenuous to point this out but it’s nevertheless true. if it’s visible, it’s not infrared.

    In response to Dr Jones statement about 650 nm.
    I spend a lot of time at the telescope. While faint hydrogen-alpha emission (656.3 nm) is invisible, I’ve certainly observed bright H-alpha sources as pinkish. Since I experience colour vision, presumably something is triggering the red channel in my brain.

    This suggests one of two explanations
    1. The red cones have a much longer sensitivity tail than is generally appreciated.

    2. There is leakage between the red channel and either green or blue which would allow H-beta or H-gamma to enter the red channel. Since I don’t confuse red green or blue very often, I don’t think this is the case.

    I have no knowledge of whether altering a persons biochemistry can change the nature of these tails.

  • ajfudge

    I’m kinda content with my eyes not seeing infra-red. It’s cool in theory, like having some kind of mutant power, but extending how I see colors, thus violating to what I’m used to seeing would probably just give me eternal headaches.

  • http://joonasmakinen.com Joonas Mäkinen

    As a biologist and medical student, I am not impressed by that argument. Basically, it was a decent overview of the visual capabilities, but the main focus of IR being impossible to “see” went pretty much along the lines of “it’s impossible because”. There was a mention of biophysics, but no reasoning whatsoever. :/

    Oh, well. There’s always bad peer review too, this being an example.