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Comment by fela | Hacker News Reader

Another interesting color fact: many birds have four independent color channels instead of our three [1]. Which means they can see a whole additional dimension of colors we cannot even imagine. I like to think how it would be to wake up one day and suddenly being able to see all those additional colors...

[1] http://en.wikipedia.org/wiki/Tetrachromacy

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Similarly, some people who have undergone eye surgery and lose part of the eye that filters it, are able to see ultra-violet light. It's theorized that this happened to Monet, and accounts for his painting of some flowers differently post cataract surgery.

I think it'd be wonderful to experience this, temporarily at least!

http://en.wikipedia.org/wiki/Aphakia

I have had my lens removed and I do experience this. To me its more annoying than exciting though. Those black light lamps used in things like club lighting are somewhat blinding to me. My glasses do filter it though.

I as well see it, like a faint hazy halo around the black light, and it really messes with my vision. I cannot go into a club anymore, nor go to haunted houses, as the black lights are really disorienting.

I have had both my lenses removed and have implants now. Since I was young when they were removed, I thought everyone saw this until a couple years ago.

This brings me to a question I've always had: What if the colors we see are specific to us? I.e., what if what I perceive as blue and you perceive as blue don't look the same to us, but because we've always been taught that that color we see is blue, our differing perceptions lead us to that conclusion?

I know I'm not explaining this correctly, I've been trying to wrap my head around it for a while.

Perhaps you're referring to "qualia"? Supposedly, it's an open question in philosophy. I'm no expert myself, but I figured I'd mention it in case you found the subject worth pursuing.

http://plato.stanford.edu/entries/qualia/

http://en.wikipedia.org/wiki/Qualia

Obligatory xkcd:

http://xkcd.com/32/

That's not an uncommon question at all. This is a single instance of a set of philosophical questions related to qualia[1], i.e., the question of subjectivity and conscious experience. Richard Dawkins stretches the question a little more by taking into consideration the experiences of other species, such as bats [2] —spatial sense through audition—, and it's not hard to find more[3][4][5]

Fun questions to ask (and hard to put into words indeed, I had my share of trouble trying this exact same thing), but I don't think we're anywhere close to answer them. At least not until we really understand what consciousness is.

[1] http://en.wikipedia.org/wiki/Qualia

[1] http://plato.stanford.edu/entries/qualia

[2] http://old.richarddawkins.net/articles/479563-sky-blue-pink-...

[3] http://www.huffingtonpost.com/mark-changizi-phd/perceiving-c...

[4] http://www.sciencedaily.com/releases/2005/10/051026082313.ht...

[5] http://www.dailymail.co.uk/news/article-2166917/We-DONT-colo...

And then there is the mantis shrimp:

http://theoatmeal.com/comics/mantis_shrimp

I never understood why we have three trichromatic vision and not tetrachomatic vision.

We have rods and three types of cones, which look like four channels to me. In very low light the cones don't fire and we see in black and white. In reasonably bright settings I can imagine that the rods saturate and we only have three useful channels. But there must be a level of light where both cones and rods are within their dynamic range. What am I missing?

The wavelength curve the rods are sensitive to spikes in the middle of all the wavelengths curves for all the cones. So I think the mental sensation of gray is pretty accurate, actually, since it is close to being just a rough measurement of all the others.

You are saying that the rods' spectral curve response is collinear with the cones. That would do the trick, but I'm a bit surprised as I don't see any reason for evolution to push you in that direction.

Do you have a reference for this? Quick googling seems to show that the rods' response curve is not, it seems to be a most sensitive at a wavelengths between the peak of the blue and green cones.

I'm not sure if this will satisfy you, but you can give this a shot:

http://en.wikipedia.org/wiki/Mesopic_vision

http://en.wikipedia.org/wiki/Purkinje_effect

>> But there must be a level of light where both cones and rods are within their dynamic range. What am I missing?

I am not sure if human vision is using one or the other. When both rods and cones are within the dynamic range, possibly response from both get utilized by the brain. I am not sure.

Spitballing here: it's not just the sensors, but what you do with them. Is the visual processing for rods handled differently than the visual processing for cones?

Actually, I feel very good about this line here:

"More than one thousand times as sensitive as the cones, they can reportedly be triggered by individual photons under optimal conditions." http://hyperphysics.phy-astr.gsu.edu/hbase/vision/rodcone.ht...

So while rods have a response curve which is similar to codes, that response curve is shifted to be a thousand times more sensitive than cones. So at any lighting level which activates the cones, your rods are just maxed out, screaming "YES, IT IS VERY BRIGHT", and you don't get any useful information out of them.

Hence, no integrated, tetra-chromatic vision.

Some women have tetrachromacy, as well. (In your quoted article, actually.)

Ah to be a tetrachromat. Interesting reference to the June 2012 study.

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