There is anecdotal evidence that the since the proteins in the human lens become opaque (absorptive) in the near infrared (search: crystallin transmission spectrum); that patients who have had their lenses removed for cataract surgery see beyond both traditional limit ends (as the polymer lens replacement has a different transmission spectrum) ... so [semi-serious-only] perhaps it would be more efficacious to have one lens removed? (no lens over a snake's thermal pits etc)
Well, the data is very noisy. The main problem is that this data doesn't have a before/after comparison. Is the 850nm light visible now or it was always visible???
It's also very difficult to make a fair comparison. The room must be the same, the light sources must be the same (a new coffeepot with a small led can ruin the experiment, removing a coffeepot because it has recently broken can ruin the experiment).
For a preliminary experiment, the before-after comparison is enough. For a serious experiment you need many voluntaries, compare the before-after signals of them all at the same time in the same experimental conditions, and double blind testing.
There is a small possibility that they are measuring "excitement" instead of light. The subject hears that they are now going to test with very near infrared light. He got exited. They measure that. Perhaps the flash makes a slight sound, perhaps the light operator makes a slight sound. (Perhaps the 850nm flash makes a sound that the other flashes don't make?)
To distinguish an extra color we would need a new type of cone cells with a different spectral response to the three types we already have (called L-, M- and S-cones). We could modify a subset of the existing cells or add new cells. If you modify the existing cells, you then need to teach the visual cortex that the signals coming from the modified cones indicate a new color. How would this be done? If you add new cone cells, you then need to add new neural pathway along the optic nerve and plug it into the visual cortex somehow. How would this be done?
On the other hand, the original experiment proposed to alter the availability of different types of vitamin A by dietary changes with the intention of modifying the spectral response of the existing photosensitive cells so that light of previously invisible wavelength would become visible. This does not increase the number of colors, but changes the range of wavelength corresponding to each color for the affected individual.
"I don’t want to be human. I want to see gamma rays, I want to hear X-rays, and I want to smell dark matter. Do you see the absurdity of what I am? I can’t even express these things properly, because I have to — I have to conceptualize complex ideas in this stupid, limiting spoken language, but I know I want to reach out with something other than these prehensile paws, and feel the solar wind of a supernova flowing over me. I’m a machine, and I can know much more, I could experience so much more, but I’m trapped in this absurd body. And why? Because my five creators thought that God wanted it that way."
That's how you do it.
Some patients who have had replacement artificial lenses develop the ability to see some portion of the UV spectrum. My mum now has this - she had lens replacement last year and following that she mentioned that a lot of things appeared more purple in some circumstances - my brother did some research and found out about the UV detection.
Wikipedia has some info: http://en.wikipedia.org/wiki/Aphakia
Younger patients get given lenses with coatings that block the UV as over time the UV can damage the retina, but they don't tend to bother with the elderly so as a bonus they get fatter rainbows.
> I have 20/11 vision with a mutation that causes me to see a lower-band of UV. It overstimulates my ocular processing and causes migraines. I wear amber glass eye glasses with +.02 diopiter lenses to help reduce this problem. Because of this, I have an absolute obsession and facination with purple objects.
I remember the original poster participated in the comment section but (sigh) I don't know how to get there.
 site:imgur.com comment uv glasses headache
It did take a bit for me to dig it up... I actually ended up having to use Google image search because I remember the guy talking about how trees looked. Without that I got a series of short uninteresting breathless YouTube videos on the topic and a whole bunch of contentless reblogging of said video that drowned out the original article.
There are similar stories with sound etc. I think some people can see near infrared, it is just question of finding them.
Related and probably equally silly idea: I've always wanted a pair of sunglasses that could tune in to different EM spectra. How far are we from that? Night vision goggles are bulky because they need external power to do the frequency shifting, right?
(Not quite the same, but in a similar vein)
"While carrots are a good source of vitamin A (which is important for healthy eyesight, skin, growth, and resisting infection), eating them won't improve vision.
The purported link between carrots and markedly acute vision is a matter of lore, not of science. And it's lore of the deliberately manufactured type.
"In World War II, Britain's air ministry spread the word that a diet of these vegetables helped pilots see Nazi bombers attacking at night. That was a lie intended to cover the real matter of what was underpinning the Royal Air Force's successes: Airborne Interception Radar, also known as AI. The secret new system pinpointed some enemy bombers before they reached the English Channel.
"British Intelligence didn't want the Germans to find out about the superior new technology helping protect the nation, so they created a rumor to afford a somewhat plausible-sounding explanation for the sudden increase in bombers being shot down. News stories began appearing in the British press about extraordinary personnel manning the defenses, including Flight Lieutenant John Cunningham, an RAF pilot dubbed "Cats Eyes" on the basis of his exceptional night vision that allowed him to spot his prey in the dark. Cunningham's abilities were chalked up to his love of carrots. Further stories claimed RAF pilots were being fed goodly amounts of this root vegetable to foster similar abilities in them...."
That's an interesting form of disinformation. I've been known to employ somewhat similar tactics myself.
How can we be sure?
Turns out I'd managed to access a significant trove of documents, admissible in court, strongly supporting my side's case.
I was in communication with several entities I suspected were communicating (directly or otherwise) with the opposing side, and while it was useful to communicate that we had significant information, detailing just what it was, or how it was obtained, was somewhat less so.
So the cover story we worked out was that we had deep connections to the black-hat online hacker community who were able to pull all kinds of random information out of the Net. Playing up the whole hacker mistique thing.
One consequence of this was opposing counsel strongly suspecting that the evidence we introduced wasn't admissible. They were rather surprised when it turned out to be very admissible. The fact that the opposing side's witnesses were shown to be markedly less than credible didn't help their side (and may have sabotaged their own case).
It was a vaguely satisfying aspect of an otherwise fairly unpleasant episode.
Edit: From this  non-scholarly source,
"The median lethal dose (LD50 value) of vitamin A injected intramuscularly
in a water-miscible form in the young monkey is 0.6 mmol (168 mg) retinol/kg
body weight. Extrapolated to a 3-kg child and a 70-kg adult, the total LD50
dose would be 1.8 mmol (500 mg) and 41 mmol (11.8 g) respectively."
Here are some absorption spectra  of crystals of various rhodopsin isomers. I'm not sure if any of these are biologically relevant isomers, but it's interesting that these were not in solution. (I suppose that since they're membrane-bound GPCRs and might be difficult to study in solution? This isn't my field of study.)
Check out some bacterial absorption spectra . Visual perception isn't limited to organisms with eyes. Or even eukaryotes, for that matter. It's actually pretty ancient .
On that note, pigment chemistry is pretty fascinating.
1. http://en.wikipedia.org/wiki/G_protein-coupled_receptor The GPCR family is really cool. A ton of our sensory perception arises from class A GPCRs. Here's a really beautiful diagram of the 7 transmembrane regions of rhodopsin: http://physrev.physiology.org/content/physrev/81/4/1659/F1.l...
2. http://www.sciencedirect.com/science/article/pii/S2210271X13... Just to cite an instance, though this one isn't vision-related.
I know that this isn't written to be read critically, but I don't know what the take-away is.
So, still red then?
All three give very bright flash when viewed via my Mac's camera (just launching Facetime with no call and pointing the remote to it).
Security cameras with IR leds are pretty bright to me. I can easily tell when the IR leds are on. Have you noticed anything like that?
Astronaut, part-time dad, professional voice actor, F1 driver, liar.