Color Vision

The short, short version:

• Human eyes are mostly cones, and some rods.
  • The rods see in black and white, with a faster "frame rate" than cones (the better to spot movement); they are much more sensitive to light in general, able to see in low-light conditions that cones cannot.
  • Cones see in color. There are three types; to oversimplify, they are red, green, and blue.
  • For any given scene, your brain receives four signals: black/white, red, green, and blue, with different signal strength for each "pixel" in your vision. If the signal from the cones is strong enough, the signal from the rods is not needed.
• That's just how our eyes work, and how the outermost lobes of the brain that receive the signals from them process it. Long before you "see" anything, the situation changes.
• After some processing, your brain converts the tri-color signal into two spectra: blue-yellow and red-green. Consider them like axes; if a color is +100 blue, it is thus -100 yellow, etc. This is known as the Opponent Process.
  • Every color humans can see can be determined from these two axes. However, it means there are colors that are real, but we cannot see them, such as "bluish-yellow" or "reddish-green".
  • You might be saying, "but I *can* see bluish-yellow...it's called green, duh". Well, let's talk about Secondary Colors.
• Secondary Colors are colors formed of some combination of red, green, and blue.
  • Red and green light, combined in roughly equal proportions, looks yellow to humans.
  • By the same token, green and blue combine into aqua, or cyan.
  • Orange is just yellow with less green and more red.
  • Purple is the combination of red and blue. Violet is closer to red, and royal purple is more blue than red, and darker in general.
• The point is, Secondary Colors only exist because our brain creates them. When you see green, you're really seeing a mix of blue and yellow. Your brain decides that looks green. It might have decided otherwise, but why should it? If you combine blue and yellow light, the mathematical average of their wavelengths is the same as a pure green light anyway.
• And that's where things get interesting. What happens when you take the average of red and blue light? You get green. And yet, we see purple.
  • Purple does not exist. It isn't a real color. By all accounts, it should look the same as green. It doesn't. Why? Because color only exists in our brains.
• And this is the nub of the matter; different brain means different color.

Elves have tetrachromatic vision: that is, they have four types of cones, instead of the human three. In our terms, those four cones respond to red, yellow-orange, greenish-blue, and violet. But that isn't the strangest thing about them; some humans are tetrachromats, too (in fact, a huge percentage of all women on the planet), and yet precious few make any use of the fourth cone, as it requires processing color entirely differently. Since humans didn't evolve with 4 cones, we can't really use them if we happen to mutate that way.

Elves aren't a mutation. All elves have tetrachromatic vision, so their brains do work that way. And thus, the weirdness: they don't use the opponent process at all.

They see Secondary Colors the same way a computer or digital camera does: as a simple, mathematical combination of wavelengths. Thus, the combination of red and yellow-orange will look particularly orange, while yellow-orange and greenish-blue will look green. Fair enough.

It is perhaps for this reason, or perhaps for some other, that the elven brain does not process the combination of red and blue (or red and violet) light as "purple". This was not discovered right away, as a truly purple object does have a distinct look from other colors, and an elf can easily pick out a purple object lying amidst red or blue ones. Humans did notice a tendency for elves to find purple shades less attractive than other colors, while they themselves find it particularly spellbinding, often coating their royals in it. Some wondered why that might be. Soon, they learned why.

The human brain organizes color into a "wheel", which accurately portrays the mixing of primary colors...until, after pure blue, we starting seeing purples. Violet, which is "more blue than blue", appears to humans to be somewhat similar to red, while royal purple is clearly less reddish. Violet could be described by a human as "closer to red than royal purple".

To an elf, this is nonsense. Asked to compare the colors of a truly red and truly violet object, an elf might say "the colors couldn't possibly be more different". And they are right, of course, from a scientific point of view. Elves describe the color violet (an even mix of pure red and pure blue) as "reddish-blue", or, more helpfully, "a sort of grayish-red-blue". Their eyes can pick out the components of red and blue, of course, but the brain does not invent a new color; rather, they see a muddy, unattractive mixture.

It is important to note that purple is not a particularly strange color on Tellandor; indeed, the Dark Star, which illuminates the night for half of each year, has been described by humans as shedding a "pale white, bluish-purple light". In fact, the Dark Star is a high-energy black body, casting a spectrum of light primarily in the blue, violet, and ultraviolet range, with just enough red and green to look ghostly white. But the "violet" a human sees in that light is a Secondary Color...and in fact, elves' highest-frequency cone responds to a higher frequency than pure blue, and thus responds more, in general, to the light of that star.

Effectively, though elves do not possess superior numbers of rods (very few, actually, compared to humans), they have far superior nightvision when the Dark Star shines, because their eyes can pick up many times more of its light. Most of the light produced by the star is simply invisible to humans; while the same is true of elves, they still get a larger share of it.

And in terms of color, well: they are seeing completely different colors than humans do. What they call "violet", they would perceive as either pure blue, or a color we cannot conceive of, depending on frequency.

Beyond the lack of a "color wheel", they simply see more colors than humans, due to their tetrachromatic vision. They can make out many more shades of color between red and yellow, and between purple and aqua. Most importantly, though, they can discern literally hundreds of times as many shades of what humans would call "green".

Elves have often been thought to have supernatural powers in handling plants; while they do have such powers, many of their abilities are simply a consequence of vision. With such subtle color separation, they can make out intricate details in leaves, grass, moss, and other green vegetation. They can see patterns indicating dehydration, disease, or inadequate supply of particular minerals. They can sense internal structure, and note inconsistencies indicating pest infestation, or fungal growth, all with the naked eye.

But this ability goes far beyond gardening. With such an eye for green shades, they can spot the slightest inconsistency in a forested environment. An elf worth his salt can spot a green caterpillar on a green snake wrapped around a green sprout concealed by green leaves in the green grass. They can make out the edges of overlapping leaves, blades of grass, or frills of moss. Their brains have evolved to handle this onslaught of information, using occlusion to enhance depth perception. In a region with ample vegetation, their depth perception and spatial awareness is far better than that of a human. This would certainly explain the ease with which they move about in the forest, and their uncanny ability with ranged weapons.

Of course, all of the above applies to High Elves; Dark Elves are a bit different. Indeed, their color separation isn't quite as good, and all the powers it grants are thus weakened. However, this is because their outermost cones are further afield from the visible spectrum of humans; their "red" is in the near infrared, and their "violet" is ultraviolet. This gives them tremendously better perception under the Dark Star, as well as infravision, a notable advantage when indoors or underground. This is believed to be the result of hundreds of generations of artificial selection, as dark elves were often made to defend darker areas (indoors, and heavy-canopied forests) where high elves felt vulnerable--those with the best darkvision survived.

It is also worthy of note that all elven eyes possess a Tapetum Lucidum, for better nightvision. It reflects only light at the lowest and highest ends of the visible spectrum, so as not to interfere with vision in the mid range (orange, yellow, green, aqua), most useful during the day. This can cause a purple reflection when light is shone upon them in the dark; to sensitive eyes, an elf hiding in darkness might be given away by the characteristic purple reflection. Elves themselves, for reasons already discussed, have difficulty making out said reflection, and didn't even realize it existed until pointed out by humans.

Dark Elves, meanwhile, having a wider spectral range, reflect infrared and ultraviolet light; the reflection is not visible to human eyes.

Fun read.

If you think elves are weird, well...you saw this coming, didn't you?

The eye of a dragon is a funny thing. Funny, in that it doesn't resemble the eye of a human or elf in the slightest, nor any reptile or avian, nor of any creature on Earth. In fact, oddly enough, a dragon's eye more closely resembles a photovoltaic cell.

The inside of a dragon's eye is coated with a lattice of monocrystalline silicon, with thin layers of silver, palladium, and titanium. It is not known how this structure can possibly be created by biological processes, but, there it is.

The silvery metals help to trap all possible light, forcing almost every photon to rebound until it is so absorbed. Thus, a dragon's eye captures a far greater percentage of the light that enters it than that of any other creature, granting it excellent nightvision. But that is far from its most amazing trait.

The light that enters the lattice, save for a tiny fraction which escapes the metal coating, is absorbed, and converted to electrical impulses, which travel straight to the dragon's brain, preserving the exact waveform of every light wave entering the eye.

Thus, a dragon has no need of trichromacy, or tetrachromacy, or any Secondary Colors at all--it sees every color exactly as it truly exists. Where humans see three colors (and mixtures of the three), and elves see four, dragons see an infinite number. Where both are limited by the density of their rods and cones in terms of visual acuity, a dragon's eye is essentially analog...it has no resolution.

It is difficult to express in words the quality of a dragon's eyesight. The only comparable device would be a mid-21st century astronomical terapixel camera, but even that cannot hold up. A dragon's eye has no lens, as it has need to focus light; it merely uses its cornea to capture as wide a field of view as possible. Draconic corneas are very bulbous, near-spherical, to capture almost a complete hemisphere each--in their natural form, that means they have nearly 360-degree vision. The brain presumably corrects the fisheye distortion.

In fact, the draconic brain is presumed to be the limiting factor to its vision. While spotting a single photon of light in complete darkness (something a dragon can do, btw) requires processing only a single signal, the far more common scenario of seeing a vast, outdoor vista lit by various suns, moons, stars, and terrestrial sources requires processing a trillion trillion trillion signals per second or more...vastly in excess of the total number of neurons in even a particularly large dragon brain.

Naturally, in a given field of near-monochromatic vision, most photons have nigh-on the same exact waveform, so they simply combine into a stronger signal of that exact color. Still, when attempting to discern greater and greater detail--essentially, when aggressively filtering out information--the draconic brain reaches its limits.

Thus, a few things a dragon can do with its vision:

• See every color in the visual spectrum
• See the entire ultraviolet spectrum, and most of the X-ray spectrum (the lower limit on wavelength is the size of the silicon lattice, about half a nanometer)
• See the entire infrared spectrum, and near into microwaves (the upper limit is the thickness of the entire lattice, a few mm for an adult dragon, up to a few cm for the largest dragons known)
• See a single photon of significantly different amplitude and/or wavelength from the surrounding field
• See the complete spectrum of any non-pure color, such as the light of a star, as opposed to a single, combined, Secondary Color
• Make out incredibly fine details, such as the hairs on a mouse's back while flying miles above it
• Notice intervals of light on the nanosecond scale (in some cases, picoseconds). For instance, a quick burst of light reflecting off a human's skin will reach the dragon's eye just slightly before the light that penetrated the skin before scattering away; a dragon can notice this time difference.

With their infinite visual gamut, dragons refuse to participate in the human/elven/dwarven habit of naming certain colors "red", "yellow", etc, except (begrudgingly) when explaining a color to one of said race. To them, it is absurd as naming each of the infinite numbers between 0 and 1...they already have names, expressed by the exact value of the number.

This, of course, figures into their disdain for the habit of other races in generalizing the Five Great Broods into colors, such as "the Red Dragonflight", or to name an individual dragon as one particular color, such as a "Green Dragon". To them, this insults both the incredible complexity of colors, sheens, and patterns of a dragon's scales (which are always unique to the dragon), and the ability of any dragon to clearly discern said colors and patterns, without the possibility of ever mistaking one dragon for another at any reasonable distance.

So yeah, long story short: dragon vision is insane. And yet...even THEY can't see purple. The ability to see the combination of red and blue light as a single color, distinct from green or grey, is unique to humans and dwarves, and less pronounced in the latter.