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page13
2009-Mar-24, 08:43 PM
When looking at electromagnetic radiation charts, the visible spectrum is depicted with the standard rainbow pattern of colours, with a steady gradation of red through to radio waves, and violet through to gamma rays.

Question 1:
Is the visible spectrum depicted with this colour variety simply because that's all that we can see and we couldn't even conceptualize what type of alternating colour banding might occur on either side?

Question 2:
If the visible spectrum is truly unique in that it's the only cross section with a variety of colours, are we to conclude that evolution has adjusted our eyes to only perceive this particular range?

Nowhere Man
2009-Mar-24, 08:55 PM
Answer 1. Pretty much.

Answer 2. Color is a phenomenon of our visual apparatus. The visible spectrum is (as I understand it) pretty much all of the EM radiation that can easily make it through our atmosphere and at the same time provide reasonable resolution. So we are adapted to what's available.

Other animals can detect infrared (pit vipers) and ultraviolet (bees). As I recall, vipers use the sense for directional location of prey; I don't think they have very good resolution in their pits. I don't know about bees.

There is an interesting article about color vision in primates in the latest Scientific American. It also delves into the reasons for red-green colorblindness.

The colors are a result of the sensors in our eyes. Look up rods and cones in an encyclopedia.

Fred

AndrewJ
2009-Mar-24, 09:28 PM
Question 2:
If the visible spectrum is truly unique in that it's the only cross section with a variety of colours, are we to conclude that evolution has adjusted our eyes to only perceive this particular range?

Yes, we can only perceive visible light and can only speculate as to what a viper or bee sees beyond this range. This begs the question "why have we only evolved the capacity to perceive a certain, limited range of the EM spectrum?". Well, a lot of solar radiation with higher frequency and energy than visible spectrum gets absorbed by our atmosphere so there wouldn't be much for us to use even if we could perceive it. Radiation with lower frequency than visible light such as infrared, microwaves and radiowaves get absorbed by water (most cannot pass through) so again there wouldn't be much point in our fishy ancestors developing a means of perceiving it. I think this last point makes the animal eye a good exhibit of natural selction and the start of life in the sea, despite ID proponents often arguing "gosh, it's so complicated, the eye could not be the result of natural processes".

mugaliens
2009-Mar-24, 09:48 PM
The continuing saga of Mugs with respect to this topic...

Please stop errantly assuming that the commonly ascribed visual ranges apply to all humans.

They do not.

speedfreek
2009-Mar-25, 12:26 AM
Mugs, as you can see further into the infrared than most of us, are we to conclude that your evolutionary lineage shares something with pit vipers? :D

dgavin
2009-Mar-25, 02:01 AM
Mug isn't the only one, but I think his vision is shifted more then mine. I had to undergo a battery of tests when I was in the Army for light sensitivity. Was getting headaches when out in the sun all day.

Turned out I have three issues.

I have roughly 2% more light rods then most people, and 1% extra color cones.

The light rods extend a bit into the area normally populated for color cones, and I have more color cones extending into the periperial vision area then normal.

The color cones in my vision are slightly off. The Red cones are shifted about 10nm deeper into the red spectrum. And the blue have about the same shift deeper into the blue spectrum.

The trouble only show up with mixed colors. Some dimmer orange colors I percieve as brown. Brighter blues seem more a little teal to me, unless they have some small about of violet to them, then I seem that as others would see blue.

However because of all the odities, I can disgunguise colors at night when there is snow on the ground and clouds are back lite by city lights, or if there are minanmal light sources close by without snow. With a full moon and some snow, I can see full color at night, and dertermin colors OK without the snow.

Which is probably why the Army loved to use me for guard duty at night some times, I could determine car colors accurately even if a car was in a dark alley and there was a 1/2 to full moon out.

Delvo
2009-Mar-25, 02:11 AM
Pit vipers don't see infra-red. The IR sensors aren't in their eyes. The "pit" in the name refers to pits in the skin on their snouts which can look a bit like nostrils, and that's where the IR sensors are. (A pit designed to not only detect radiation but also determine the direction of its origin is one of the earliest stages of evolution toward eyes, but it isn't an eye.) So they detect the IR with their skin. Your skin can feel IR radiation, too, just not with as much sensitivity or directional precision.

Jeff Root
2009-Mar-25, 05:04 PM
page13,

As Nowhere Man said, colors are a result of the sensors in our eyes
being stimulated. Colors do not exist in the electromagnetic radiation itself.

All electromagnetic radiation is essentially identical. A gamma ray is the
same as a radio wave. They differ in wavelength/frequency/energy, but
that is not a fundamental difference. It is like water waves of different
wavelengths-- they are all fundamentally the same.

However, different wavelengths/frequencies/energies interact with
different atoms and molecules. A molecule of oxygen in the air, for
example, absorbs some wavelengths and transmits other wavelengths.
Same thing for a molecule of pigment in a light-sensitive color receptor
in your eye. It absorbs some wavelengths and transmits others. The
brain inteprets the combinations of signals from different color receptors
in the eyes as different colors. Light, color receptors in the eyes, and
processing done by the brain are all required to perceive colors.

As AndrewJ said, the range of wavelengths that can get through the
atmosphere is a primary cause of the range of wavelengths that
we can see. Eyes developed to see the light that was useful to see.
The more useful a range of wavelengths, the more likely that eyes
would develop to see in that range.

Different animals have different numbers of color receptors, and divide
up the spectrum differently, depending on the receptors that developed
in the particular envronment the animal lived in. If I recall correctly,
fish have only two color receptors.

A chemical in the receptor absorbs more light in one range of wavelengths
than it absorbs outside that range, making the receptor sensitive to that
range of wavelengths. Nature can't guarantee an animal that it will make
a chemical that will give it the ability to see a particular part of the light
spectrum, even if that part of the spectrum is present in the animal's
environment and would be very useful to the animal. Evolution isn't able
to plan ahead. It can only make what the available materials allow. So
there is no reason to think that unrelated animals would have similar eyes
or similar visual processing in their brains, or that they would see colors
in anything like the same way.

Humans can plan ahead, though, and figure out ways to make cameras
and spectroscopes and other devices that can distinguish different
wavelengths/frequencies/energies of light throughout the entire spectrum,
and convert that into numerical data or images or sounds or other forms
of output that we can use. The spectrum can be divided up into millions
of different "colors" in this way.

-- Jeff, in Minneapolis

mugaliens
2009-Mar-25, 11:40 PM
Mug isn't the only one, but I think his vision is shifted more then mine. I had to undergo a battery of tests when I was in the Army for light sensitivity. Was getting headaches when out in the sun all day.

Turned out I have three issues.

I have roughly 2% more light rods then most people, and 1% extra color cones.

The light rods extend a bit into the area normally populated for color cones, and I have more color cones extending into the periperial vision area then normal.

The color cones in my vision are slightly off. The Red cones are shifted about 10nm deeper into the red spectrum. And the blue have about the same shift deeper into the blue spectrum.

The trouble only show up with mixed colors. Some dimmer orange colors I percieve as brown. Brighter blues seem more a little teal to me, unless they have some small about of violet to them, then I seem that as others would see blue.

However because of all the odities, I can disgunguise colors at night when there is snow on the ground and clouds are back lite by city lights, or if there are minanmal light sources close by without snow. With a full moon and some snow, I can see full color at night, and dertermin colors OK without the snow.

Which is probably why the Army loved to use me for guard duty at night some times, I could determine car colors accurately even if a car was in a dark alley and there was a 1/2 to full moon out.

I found your comments to be very intriguing, dgavin! And familiar. I'm definately a sunglass-wearing fool... I don't have anywhere near the color resolution at night as I do in proper lighting, but it's there, and able to see the full spectrum. Except in sodium vapor lighting under an overcast sky... To me, that's the stomach-churning equivalent of a green fridge light - driving in them makes me slightly nauseous.

JohnD
2009-Mar-26, 12:35 AM
dgavin,
I'm not calling you a liar, but this is supposed to be a scientific website and the "Science & Technology" Forum.

You have "roughly 2% more light rods then most people, and 1% extra color cones."
But the reason why humans have poor night colour vision is that cones are too insensitive. Rods are about one thousand times more sensitive to blue light than cones.
I fear that a few more rods or cones cannot account for "full color" night vision.

And your 'red' cones are "shifted about 10nm deeper into the red spectrum." 'Red' cones have maximum sensitivity at 575 nm, a wavelength that we would usually describe as 'yellow/orange', and their sensitivity extends, though diminished, as far as 700nm. So a 10nm shift through normal variation or mutation is trivial, as is any shift in the blue cones.

I don't doubt your excellent night vision. But seeing well and in colour in bright moonlight and snow, when the light intensity is so high, and much higher than, say, a new moon on grassland, is something that many humans can do.
See: http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0003711
NB: and horses!

There is considerable variation in the human phenotype, apart from the obvious hair, eye and skin colour. I lack a palmaris longus muscle in either forearm, a lack shared with 7-16% of the population. I don't think it means I am functionally different from anyone.

John

dgavin
2009-Mar-26, 01:02 AM
dgavin,
I'm not calling you a liar, but this is supposed to be a scientific website and the "Science & Technology" Forum.

You have "roughly 2% more light rods then most people, and 1% extra color cones."
But the reason why humans have poor night colour vision is that cones are too insensitive. Rods are about one thousand times more sensitive to blue light than cones.
I fear that a few more rods or cones cannot account for "full color" night vision.

And your 'red' cones are "shifted about 10nm deeper into the red spectrum." 'Red' cones have maximum sensitivity at 575 nm, a wavelength that we would usually describe as 'yellow/orange', and their sensitivity extends, though diminished, as far as 700nm. So a 10nm shift through normal variation or mutation is trivial, as is any shift in the blue cones.

I don't doubt your excellent night vision. But seeing well and in colour in bright moonlight and snow, when the light intensity is so high, and much higher than, say, a new moon on grassland, is something that many humans can do.
See: http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0003711
NB: and horses!

There is considerable variation in the human phenotype, apart from the obvious hair, eye and skin colour. I lack a palmaris longus muscle in either forearm, a lack shared with 7-16% of the population. I don't think it means I am functionally different from anyone.

John

I don't think you understood my post well, I mentioned I could distinguish colors down to 1/2 moon. If I look at something long enough, I can determine the color. It's hard to explain otherwise. It's just in Snow, or bright night/snowy conditions I can see full color without conscious effort.

The 2% and 1% was what was explained to me from all the testing I went through, and the slight shifting. Again I stated it wasn't as signiticant as mug's.

I had(have) a permanent medical profile for light sesitivity for all this when I was in the army, so it's scientific and documented. The battery of the test results probably exist in some army records center too.

George
2009-Mar-26, 02:58 AM
I don't think you understood my post well, I mentioned I could distinguish colors down to 1/2 moon. If I look at something long enough, I can determine the color. It's hard to explain otherwise. It's just in Snow, or bright night/snowy conditions I can see full color without conscious effort.

The 2% and 1% was what was explained to me from all the testing I went through, and the slight shifting. Again I stated it wasn't as signiticant as mug's.

I had(have) a permanent medical profile for light sesitivity for all this when I was in the army, so it's scientific and documented. The battery of the test results probably exist in some army records center too.
Any idea what size your pupil size is at night? Yours may allow more light than most, perhaps.

You may also have a much higher conversion rate of electrical signal to photons. Without checking, I think the typical conversion rate is one photon reaction for about every 1000 photons, though we are capable of seeing a single photon, just not every one.

Eye sensitivity does vary. Some can see UV light at around 320 nm, where about 400 nm seems to be closer to the normal limit.

Jens
2009-Mar-26, 03:02 AM
I don't think you understood my post well, I mentioned I could distinguish colors down to 1/2 moon.

But I think the main point that JohnD was making is that there is diversity in human genotypes and abilities. Some people can run significantly faster than others. Some people can eat more without getting fat. Some people can't read small letters. I think the point is that some variability is expected with night vision as well.

jlhredshift
2009-Mar-26, 04:12 AM
I found your comments to be very intriguing, dgavin! And familiar. I'm definately a sunglass-wearing fool... I don't have anywhere near the color resolution at night as I do in proper lighting, but it's there, and able to see the full spectrum. Except in sodium vapor lighting under an overcast sky... To me, that's the stomach-churning equivalent of a green fridge light - driving in them makes me slightly nauseous.

I do not know what normal is but my peripheral vision goes to almost 200 degrees in color. Which was a definite advantage during my racing days.

dgavin
2009-Mar-26, 02:06 PM
But I think the main point that JohnD was making is that there is diversity in human genotypes and abilities. Some people can run significantly faster than others. Some people can eat more without getting fat. Some people can't read small letters. I think the point is that some variability is expected with night vision as well.

Actually from the first sentence, seemed more like he was questioning my credibility. Hence mentioning it's been recorded in military records some place.

Yes variability is a very true point. So is age...

Age however seems to take it's tool on those of us with slightly different vision as well. Bleh. Up age 30 I could read the micro-printing on most anything. Now I can't...

Althought it's proabably a topic for a different thread, I'm wondering now if there some statistics on what sort of deviations from normal vision there are out there. Color blindness, color shifting, less/more rods cones...etc...

dgavin
2009-Mar-26, 02:17 PM
Any idea what size your pupil size is at night? Yours may allow more light than most, perhaps.

You may also have a much higher conversion rate of electrical signal to photons. Without checking, I think the typical conversion rate is one photon reaction for about every 1000 photons, though we are capable of seeing a single photon, just not every one.

Eye sensitivity does vary. Some can see UV light at around 320 nm, where about 400 nm seems to be closer to the normal limit.

Pupils are normal, although the iris's are tri-color.

You could be right about it being better conversion rate...the optomologist and the optometrist that subjected to me to all the testing attributed my sensitivity to extra rods and cones.

But I'm almost certain they did not perform any sort of rod/cone inventory.

So your explanation might also be right. Never thought of that before.