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Eigengrau (wikipedia.org)
217 points by ekpyrotic on June 23, 2013 | hide | past | favorite | 68 comments

I use to do some spelunking and on many occasions lost light while underground (usually failed batteries, one time my light took a bad hit. Thankfully I always had backups). I wouldn't really describe the color as "gray" though, there is too much randomly colored static for that. More of a very dark soupy brown. Sort of like construction paper perhaps.

Definitely mirrors my experience.

For full sensory deprivation this becomes especially trippy when you can only hear the white noise of rushing water and you're numb from cold.

Slight correction: the colour of rushing water's noise is not white. More like Brownian (http://en.wikipedia.org/wiki/Brownian_noise). White noise is rather jarring on the ear.

Or you can find yourself an isolation tank.

Are there tanks engineered for those with tinnitus? Sensory deprivation + tinnitus only means screamingly loud ringing for me - nightmarish.

This is a total aside, but I've always wondered: is the ringing a repeating waveform? If you could discover its structure through trial and error (e.g, cycling through pure tones and looking for beat frequencies), could you create an anti-ringing real waveform that nullifies the tinnitus? In other words make a hearing aide + your ear physiology act like a noise cancelling headphone, at least as far as your auditory nerves are concerned.

My limited understanding is that it is from one of the hairs in your inner ear being bent or broken in some way - the hair itself doesn't move, but since it's bent in the way airwaves could are able to bend it momentarily, the brain interprets it as it being in that momentary state permanently. Waveform cancellation happens at a physical level - it wouldn't "unbend" the hair as the hair isn't actually moving.

I don't actually know though, this is just my understanding.

Some people get surgery to cut their cochlear nerve, and they still hear it. Tinnitus often originates in the brain.

You can't cancel something (using sound) that has origins in a deeper area of the hearing system (usually the nerves or the brain)

I'd be quite keen to hear how they determined that #16161D is the color of Eigengrau. Stick somebody in a pitch black room, show him various shades of grey on an illuminated display, stop when indistinguishable? But alas, the [citation needed] suggests it was simply pulled out of someone's Eigengrau-colored orifice...

@coldarchon - you are hell-banned.

How could you tell?

Turn on "showdead" in your profile.

I wonder how that is connected to phenomena like visual snow. Many people including me see similar effects not only in dark environments but troughout the day. Some resembling swarms of color, some seeing snow or something that resembles television static. For me there is no evenly colored surface anymore because a very faint swarm of colors washes over them.

It affects my vision rather negatively and the darkness magnifies the effect immensely making it hard for me to be aware of the countours of objects.

There are forums on the net were people experiment with various drugs with bizarre effects, spontaneous healing or no improvement at all were others see immediate effects.

My doctor send me to the optometrist, his assistant wondered why he didn't send me to a neurologist, the optometrist dismissed it because there wasn't anything wrong with my eyes.

> For me there is no evenly colored surface anymore because a very faint swarm of colors washes over them.

Take a look at https://en.wikipedia.org/wiki/Entoptic_phenomenon

If you are having progressive vision problems that worsen your quality of life, consider being persistent in voicing your concerns and perhaps visit an ophthalmologist.

I have the exact same thing which started about half a year ago in a moment of panic. Since then i have seen countless doctors and nobody found anything. But it still impacting my vision and i had some anxiety issues from it in the beginning because in some moments where its worse (in the dark) i was getting some kind of panic from it. It was really freaking me out but i have learned to life with it like my tinnitus as nobody seems to have an explanation other than psychological issues.

For me its like constant tv-like static that is mostly transparent but makes the outlines of everything slightly blurry. Ranges from almost not visible in good natural lighting conditions to very visible flicker in dark enviroments or places with lots of artifical light sources.

Never did any illegal drugs, dont smoke, dont drink alot of alcohol and workout regularly. Brain scan and everything was OK.

It started after 2 years of psychologically very taxing situations like a failed startup, failed long-term relationship etc. Dont know if its related to that, but it could...i am fine now and its still there though.

Another reminder to not constanly overwork/overstress yourself, many people dont realize in what ways your soul and body might react that you might not be able to reverse.

from my experience the aspect of constantly worrying makes it more annoying than it is. I can often go weeks without noticing it (can't remember not having it, dunno when it started, might be related to anxiety/panic one way or the other). Looking at bright single colored things makes me uneasy because of it though, eg the sky or white walls.

I wonder if there's any reasonable way to tell how much interpersonal difference is psychological vs. physical. I feel like it has a large impact on my sense of the world, when you combine a high myopia, a quite large number of floaters always present, and a rather striking version of the "blue field entoptic phenomenon". But is that a feature of my eyes, brain, or both?

IANAD but that sounds serious to me. Visual field distortions are often brain issues. I would go to a neurologist to be sure. Could be a tumor applying pressure to your optic nerve or something.

From a terminology standpoint, usually when people talk about visual field deficits, they are referring to reductions in a visual field, rather than unusual visual phenomena within an otherwise functional visual field.

Anyway, visual field deficits can be brain-lesion-driven, as you say (e.g., the classic bitemporal hemianopsia in pituitary tumors).

I've became aware of it about 15 years ago, so it would probably have already killed me if it was anything like that.

No, not necessarily. I've met someone who had a benign brain tumor -- it caused them to have mood swings, but was not in any danger of spreading.

In their case the doctors didn't remove it because the operation would have been more dangerous than the tumor itself, and the symptoms were not too severe. But it's obviously better to be aware of such things.

My wife had a growth removed from her brain a few years ago. Apparently it had quietly sat around since she was a child, not doing anything, until it decided to get its shit together and try to kill her.

ElongatedTowel ought to go to the doctor and deal with a few weeks of feeling like an embarrassed jerk by demanding that they scan his/her brain.

I suffer from visual snow and also have floaters. You learn to ignore the static after a while but it is always there if you focus - looking at plain surfaces (e.g. blue sky) makes it very obvious. And as you said, it drastically affects my vision in darkness (think of grainy CCTV footage). I haven't done drugs and don't suffer from migraines which are thought to be correlated. Apparently it is also correlated with Tinnitus but I haven't been able to self-diagnose that.

For the longest time, I wondered if people saw a "static" overlay like I do. Talked to my optometrist about it last time and he wasn't aware of this condition. Googled it later and there is some research starting on the subject: http://www.eyeonvision.org/

Have the same thing (as detailed in my other post to this parent) and i also suffer from Tinnitus. Interesting that some people on HN seem to have the same issues, even if its just for the "i am not alone with this" feeling. You kind of loose faith in yourself if nobody around you, not even the doctors, has ever heard of what you try to explain.

I had no idea this wasn't normal. I might also have Tinnitus. I can't imagine how the world looks and sounds to normal people, must be great!

Did you use any mind-altering substances(excluding alcohol/tabacco)? I guess the answer is no, because you probably would mention it in your original post. But some of them may produce such effects -- that's why I am asking

I am affected as well and I have taken anything apart from those, did not even ever smoke weed.

No, apart from alcohol I've never taken anything.

Because visual snow has nothing to do with your eyes. More related to migraines than anything.

I've never had a migraine in my life, but have constant visual snow since I was a child (as I can remember having conversations with adults and being surprised they didn't see the same way I did).

I meant related to the processes behind migraines (specifically migraine aura). Not that migraines cause visual snow. IIRC, there is currently research being done on visual snow at the UCSF.

Wait, isn't that normal? Are you saying that some people - most people, even?! - don't see the light static when they stare at a clear blue sky?

As far as I know they do. See here https://en.wikipedia.org/wiki/Blue_field_entoptic_phenomenon

But I see it everywhere and probably far more pronounced than what is described in the article.

I've experienced this any number of times, mostly when backpacking in the Adirondacks in overcast conditions. I've woken up in the middle of the night with no feeling of vision at all -- no sense of light or dark. It can be extremely disconcerting and similar to the feeling of drowning, for anyone who's also experienced that.

The article also suggests the phenomenon is temperature related, which I'd confirm. The times I've approached true panic for feeling "blind" have been between -20 and 30 degrees Fahrenheit, while I've always seen more of a mid to dark brown at warmer temperatures, from 50F up.

I'm pretty sure the temperature of the rhodopsin in your eye was above 30 degrees Fahrenheit :)

A toad's eye temperature can vary because it's cold-blooded. If humans' experience of eigengrau varies with outside temperature, well that's interesting and deserves study.

Sure. I assume I'd be truly blind if the fluid in my eye eve went below zero C. I'm talking about the perception only.

I found wikipedia's section on "The mathematics of color perception" very, err, illuminating. It made me realize just how complicated the topic is...



There is a video of Feynman presenting this lecture somewhere, sorry I couldn't find it.

Thanks -- I'd previously read a passage where Feynman talks about the idea of "negative" colors, but I somehow had missed that there was a whole chapter in the Lectures about vision!

A question also comes on why humans have three color channels. Or more generally, why is the number of cones relatively small (some species have more than three).

While I cannot find the reference, some researchers recorded full visible-range spectrum for a very large number of naturally occurring objects. Then they performed principle components analysis of these spectra and found that for naturally occurring reflection spectra, nearly all signal energy is recovered with a small number of independent components like three or four. In other words, the spectra of naturally occurring materials does not vary as widely as it could to exercise the full Hilbert space available. A downside of having a larger number of cones is of course that the percentage area available to each cone will be less, so a higher density of cells would be needed to maintain the resolution and color perception under dark will suffer more. The nature then has chosen a near optimal number of cone types for vision.

One issue I had discovered with the above study was that it was possibly cyclic. The database of spectra they used did not had too many samples of (different) objects with the same apparent colors since the latter was collected primarily to count the number of human-distinguishable colors occurring naturally in nature.

If the number of primary colors visible to humans were significantly larger, I can on the very least say that TVs and printers would have been significantly different than what they are, if at all they would have been practical.

The above however does not answer the question of the electromagnetic radiation frequency span sensed by the eyes. In other words, why is the visible range not wider than what it is. Again, some animals do have a wider range. Had the visible range been wider, it may have required a larger number of primary colors to cover the expanded Hilbert space. What a physicist once told me is that the range of frequencies that are visible to humans and animals correlates very well to the frequency range under which water is transparent. See [1]. This according to him offers a solid indication that life originated in water.

A few more interesting thoughts:

1. Figure out what determines the shape of the locus of the spectrum (monochromatic) colors on the color chart [2]. It is an interesting exercise to derive this locus from the measurements of the spectral responses of the three cone types. Note that the outer boundary of the color chart has a straight line bottom with purple to magenta in the middle. While the non-straight boundaries span monochromatic colors, the colors on the straight edge at the bottom cannot be monochromatic. Figure out why.

2. A question comes if the spectral responses of the cones could have been such that the above locus would have concavities. I am not sure of the answer, though am sure colors outside of the locus but within its convex hull would still have been visible.

[1] http://en.wikipedia.org/wiki/File:Absorption_spectrum_of_liq...

[2] http://en.wikipedia.org/wiki/File:Cie_Chart_with_sRGB_gamut_...

What's more fun when you constrain to only humans is that nearly all other mammals are dichromats. Old world primates then re-evolved trichromic vision.

This provides some reminder that evolutionary pressure does not select for optimal coverage of the EM spectrum, but for the portion of the EM spectrum which will provide advantages.

Excellent post, but:

> This according to him offers a solid indication that life originated in water.

Huh? Why assume that eye designs should have evolved underwater then remained unchanged for the hundreds of millions of years that life has been on land? Eyes have actually re-evolved independently several times (IIRC).

> What a physicist once told me is that the range of frequencies that are visible to humans and animals correlates very well to the frequency range under which water is transparent.

I always thought that it was related to the spectrum of sunlight.

Well, that too. While UV is nearly absent in sunlight at the sea level, there still is a lot of energy in infrared that is not visible to the human eyes. See here for examples: http://en.wikipedia.org/wiki/Infrared_photography

It's probably just a matter of trade-offs. The visible range does cover the peak energy of the spectrum of sunlight, and covering more of the infrared may just not be worth the cost of a more complicated eye.

It would be interesting to see some type of measure of the information content of adding more infrared in typical nature scenes.

Let's post random wikipedia articles without commentary, turning HN into /r/todayilearned.

So generally, I'd agree with you. But the thing is, this is so much more interesting than another 30 articles and links to tweets about Edward Snowden's current location that I'm perfectly happy to upvote it. At least I've learned something from the article, and something about how my body works, no less. And then something more from the HN discussion, in which jlgreco and agf posted interesting anecdotal about the topic.

Go ahead, post all random wikipedia articles you want. The cool thing is how only the most interesting ones will be upvoted. Now that I think of it, that could be a neat small script to hack.. post random wiki articles on HN, let HN-ers upvote the good ones, and only read the best ranked ones.

Voting works well with small-to-medium communities of readers invested in the quality of discussion, but breaks down in large groups. Look at some of the larger subreddits - people in the comments complain about the quality of frontpage articles because the voting group becomes much larger than the commenting/discussion group.

I wonder what's going to be the next big innovation in filtering the firehose?

There are more interesting algebraic operations you can do on the voting vector than just adding it up..

Another interesting color is Cosmic Latte: http://en.wikipedia.org/wiki/Cosmic_latte

Didn't Goethe describe this in his Theory of Color? Amazing physical/physiological study of sight.

I find the Eigengrau to be a very relaxing color and I use it as the background of my desktop. It always puzzled me that it's not a pure grey but it has a little blue. I thought he had more sense that there was a little red because of the minimal amount of light that passes through the capillaries of the eyelids.

I suffer from epilepsy and often I see scintillating scotoma, visual snow and other strange light phenomena. Given this I came to the conclusion that my brain associate this color to a quiet mental state.

1) Close eyes. 2) Point flashlight at eyes.

I observe that the intensity of the "Eigengrau" depends on how tightly I close my eyes. With the flashlight, the image is clearly more red than gray. This could explain some reports of "brown", to the extent that brown is a dark red.

when it says that the half-life of the rhodopsin molecule is about 420 years, does that mean that if we would live that long, half of our rhodopsin will be gone? how would that affect our eyesight?

Your rhodopsin get replenished.

How did they decide on the RGB values? Or did someone just make that up?


this isn't particularly surprising. every photo-sensor known to man has "dark" noise and it is indeed temperature dependent. noise goes up for a fixed temperature for sensors that are sensitive to longer wavelengths, so the fact that people report a more brownish color makes more sense than perfectly grey to me. the sensors in your eyes that are sensitive to deep red will be noisier than ones sensitive to blue.

Why is this #1 on the front page? And how is it useful? I think a common pitfall for techies is amassing lots of useless knowledge (a habit I have weaned myself off over the last few years).

I kinda feel like useless knowledge is an oxymoron.

If knowledge about our world is a pitfall, then I'm happy to seek out new traps.

Do you know how useless I find knowledge about Rails? Utility is relative, and sometimes things are just interesting.

I don't know why it's #1 though. Maybe pg's skewing the numbers against all the NSA content? Maybe people are just upvoting anything that's not NSA/Snowden/etc?

How did you wean this habit, and has it made things better for you?

German adds mystique.

Neat find! I really dislike the feeling that 'seeing' this causes. I can only describe it as helpless and vulnerable, while I search for light.

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