UV vision

[Yansuf]

What basis is there for saying that you can see at night by UV from the moon or stars?

[Steve Long]

This isn't a rules question, it's a scientific question, so I've moved it to the "Discussion" board so anyone who's interested can respond.

[lucky]

Posting this question on Wikipedia yielded this result:

"Night Vision is the ability to see, whether through biological or technological means, in a dark environment. Most instances, whether biological or technological, use a combination of two approaches: enhanced spectral range, and enhanced intensity range.

(...)

Enhanced spectral range techniques make the viewer sensitive to types of light that would be invisible to a human observer. Human vision is confined to a small portion of the electromagnetic spectrum called visible light. Enhanced spectral range allows the viewer to take advantage of non-visible sources of electromagnetic radiation (such as near-infrared or UV radiation)."

[CBikle]

I was actually thinking of starting a thread about U.V vision.

For 10+ years, I've run a character with it in a Champs game with multiple GMs.

To this day, I've never been able to use it beyond sometimes being able to see in dark conditions.

How do other players use it in their games and what kind of techno-babble do they use to rationalize those uses ?

[Trebuchet]

Ultraviolet Vision works in RPGs solely because a certain gentleman named E. Gary Gygax decided elves could see in the dark using UV vision in his original Dungeons & Dragons™ game. There is no other scientific basis for UV light providing night vision. While the stars do emit UV light; that ultraviolet light is no brighter than normal starlight is. Seeing with UV light at night would require artificial UV light sources such as UV flashlights (which do exist; there are even UV LEDs).

In our Champions campaign we allow UV to work as night vision mostly as an homage to Gygax; sort of like ordinary eyeglasses providing an impenetrable disguise for superheroes.

[ghost-angel]

We use UV to allow a character to have some visual input whenever there is UV Light to see by. Since we don't really know what UV Light input might be like for us we kind of make it up a bit - decent details, no color since that's part of the visible spectrum.

We try not to think too hard about it though.

[Dust Raven]

UV is an additional chunk of the EMS, meaning a character with it can see more light than characters without it. More light = more can be seen. I don't really know if the physics of this really work, but that's the logic I use.

There are people that can see into the UV (mostly because their cornias have been removed), a google search might reveal more about how a "normal" human actually sees at night with such eyes.

[Cancer]

Strictly speaking, the ability to see UV would mean you had an additional, UV-sensitive pigment in your retina. That would mean you had an additional dimension in your perceptive color space.

In a fantasy campaign, that'd give you some bonuses for sight perception. Assuming only you had that, then you'd have the advantage that everyone else in the world was (in a sense) color-blind. A lot of camoflage just wouldn't work against your vision ... lots of pigments that look the same in the visible have different reflectivity in the UV. Also, cut vegetation changes color as the pigments in it break down as the tissue dies ... I don't know if the UV reflectance changes faster or slower than the reflectance in the visible region, but you could posit that if you wanted.

In a modern campaign, this would be more so. LOTS of "white" pigments are actually suble fluorescents that absorb well in the UV and re-radiate in the visible (typically in the blue). (This is why under "black light" so many white clothing items glow blue.) If you're equipped to see UV, you would be able to distinguish these things easily, without the use of a srong enough UV source to make the fluorescence stand out in the visible.

[Bloodstone]

Ok, I'll admit that it's been years and multiple additions, but didn't elves have INFRAvision? ULTRAvision came some time later. Could be wrong or I could just not be remembering far enough back. I did essentially get me start with AD&D, as opposed to the white box, but I've read tons of stuff from that era...

back to the core discussion:

In any event, if you don't like passive UV vision allowing you to see at night, you can always converrt it to an active sense instead. This would allow you to emit UV light that you could see by and it would work in caves and other completly dark areas. The down side is, others could possibly see you if they have some way of detecting the UV light you are sending out. But against most foes, the emmissions would be invisible.

Also, if your eyes are adapted to actully see at night via passive UV vision you should be completly blinded by normal sunlight. Unless you have away to shut it off of course. For example, while some animals and insects can see into the UV spectrum, they cannot use it to see at night.

[Dr. Anomaly]

That's correct...originally elves and dwarves had infravision. (Though I must admit I went and pulled my Basic boxed set just to double-check.)

[Deejmeister]

The Drow had ultravision...

[Lord Liaden]

The Drow had ultravision...

Indeed they did. The original Vault of the Drow, the giant underground cavern containing their city, was also covered in some kind of fungus which emitted UV light, so that was a great practical benefit to them.

[prestidigitator]

Certain things are more visible in the ultraviolet spectrum. Insects use it to see many flowers that are ultraviolet colored (as well as often--but not always--having distinct visible spectrum coloration). It is used in forensics to detect biological material and certain chemicals.

Note that compared to the frequency/wavelength range of the visible spectrum, the ultraviolet spectrum is huge, so depending on how much of the UV spectrum characters with UV Vision can see, they might: 1.) be able to see well at night because of the much greater range of frequencies they can perceive--and thus the greater intensity of light their eyes respond to--and 2.) be able to see much more detail in some situations.

For mention of other applications see: http://en.wikipedia.org/wiki/Ultraviolet

[pinecone]

I was actually thinking of starting a thread about U.V vision.

For 10+ years, I've run a character with it in a Champs game with multiple GMs.

To this day, I've never been able to use it beyond sometimes being able to see in dark conditions.

How do other players use it in their games and what kind of techno-babble do they use to rationalize those uses ?
If you watch the inumrable CSI spinoffs you'll see a passel of uses for UV vision, it lets you spot things that are invisable in the normal spectrum, but are florecent in UV...for example, no one knows why...but all scorpions are florecent in UV......so use it as a mobile forensic tool, called "my cool sense" to spot chemical traces and stuff like that....

[Zeropoint]

Nitpick: Fluorescent objects would be darker in the UV than normal objects, because they are absorbing the UV light, not reflecting it. If you could see both normal and UV spectra, I would guess that fluorescent objects would appear unnaturally "reddish" as they converted higher frequencies to lower.

[Yansuf]

Yes, I remember Gary putting that in D&D. He basically used it as nightvision.
UV is what causes sunburn, it won't help you to see at night unless you are using an artificial UV source, like the old (1950's) metascope did.
The answer that we keep it as a tribute to Gary is the best I've heard.

[prestidigitator]

Nitpick: Fluorescent objects would be darker in the UV than normal objects, because they are absorbing the UV light, not reflecting it. If you could see both normal and UV spectra, I would guess that fluorescent objects would appear unnaturally "reddish" as they converted higher frequencies to lower.
True, but there are applications for which the very low end of the near ultraviolet spectrum is used, which can be seen a bit at high intensities by the human eye. There are also things we currently detect with a camera operating in the ultraviolet rather than getting them to flourese in visible colors by irradiating them with ultraviolet light.

[input.jack]

Our campaigns have two kinds of UV vision:

Passive UV (5 pts): Allows the character to see as well in normal darkness as a normal person can at twilight, so long as there is some ambient ultraviolet light, or weak light. This would include moonlight, or a moonless night with stars out, or pretty much any time there is even the faintest amount of light. In practice, this means that unless youre in a totally enclosed space, like the interior of a building, or in a mineshaft, youre fine. Passive UV is rather "grainy" and while you can see whats what, you take a small (-2) penalty to Per rolls to see details.

Active UV (10 pts). The character not only sees UV light, but is also capable of emitting UV light in small amounts through natural phosphoresence. The character can see as well as a normal person in good light, regardless of the lighting conditions. (Smoke is a totally different matter). The character can be in a large trunk at the bottom of a mineshaft at night during a total eclipse, and still read the ingredients on the back of the wrapper of their twinkies.

[Frenchman]

I have always ruled that UV perception was just about as useful as IR perception. UV perception lets some things stand out like Shaq in Japan - such as organic fluids (even when dried), most insects, crushed plants, etc... Meaning it can be used to quickly (and easily) identify most sorts of undead, and deny them and most insect-like critters their sneakiness in the dark. Many plants and animals have patterns on them which are only visible in the UV spectrum, so I occasionally allow a player with UV a small (+1) bonus to appropriate KS rolls to recognize them.
UV perception can be used to track (either with the sense adder, or as a bonus to the skill) people who have walked through grass (crushed/damaged plants stand out in UV) or stepped in a puddle (ditto for mud). UV isn't hindered by the things that would foul most other senses (stepping in water to lose scent, walking on grass to dissipate heat quickly), but it is interfered with by the much simpler (but less obvious) method of walking on dry, level, hard ground (like concrete) long enough to wear the moisture off the bottoms of your shoes.

I personally like it when I see a character choose UV or IR rather than nightvision, and go out of my way to make sure they get some use out of it. Same goes for Sub/Ultrasonic hearing and other unusual senses that we (as normal humans) have difficulty wrapping our heads around and finding uses for.

[DangerousDan]

If you watch the inumrable CSI spinoffs you'll see a passel of uses for UV vision, it lets you spot things that are invisable in the normal spectrum, but are florecent in UV...for example, no one knows why...but all scorpions are florecent in UV......so use it as a mobile forensic tool, called "my cool sense" to spot chemical traces and stuff like that....

This isn't an example of UV vision, but of Images, only to create UV light.

Seeing things that fluoresce when exposed to UV light uses normal vision, not UV vision. UV vision would allow one to see the UV reflecting off of things that do not fluoresce. You might notice that the UV light sources the CSIs carry have an orange piece of plastic that the CSI looks through. This blocks the UV light from reaching the CSI's eyes.

Having (passive) UV vision enable characters to see in the dark is an arbitrary game mechanic that has little relation to reality. In the real world, there is a large amount of UV in daylight sunshine, but very little UV at night even with full moonlight. All fluorescent lights emit some UV, and flames do as well. Bloodstone is quite right in pointing out that UV vision that could allow one to see at night would be useless in daylight.


Also, if your eyes are adapted to actully see at night via passive UV vision you should be completly blinded by normal sunlight. Unless you have away to shut it off of course. For example, while some animals and insects can see into the UV spectrum, they cannot use it to see at night.

Odd note: years ago, my family had a circular fluorescent light in the kitchen ceiling that would not start unless there was a minimum amount of UV light shining on it. At night, you could turn the switch and wait in the dark for hours. Shine a bright flashlight directly on the bulb and you got nothing. Run the toaster oven at full power, and still you got nothing. But light a burner on the stove or strike a match or light a cigarette lighter and the lamp would spark right up.

[Ndreare]

Just a little note for you to think of on this topic.

Infrared: Does not pick up heat or cold or any thing like it. What Infrared does is allow detection a very broad spectrum of electromagnetic radiation emitted from the transfer or energy from one source to another. IR is incredibly useful in things like inspecting metals, structures and dark areas. As a structure with a flaw in it will have different impedance zones and the heat of things going through and near them will change IR radiation will be emitted. This means you can see very well in perfect darkness. I have done quite a bit of MSHA work (Mine Safety and Hazard Awareness). You will also be able to see little flaws. However there are limits to perception. As in if you are at a sensitivity (gain) level to be able to see flaws in structures and in caves then a source like fire (with tons of heat transfer to the air) will potentially blind you and damage your eyes (equipment). In our society we use IR technology for inspecting Electrical wiring, in the air, buried and behind walls. We also use it for looking at concrete pylons for fishers and breaks. IR runs from ~10,000,000 – 7,000 Angstroms

UV much like IR is also very useful in many the same ways however its reasons are a little different. What we see as humans is less than 1% of the EM spectrum. Well as fate would have it we have the ability to create equipment that lets us see into the UV spectrum which is also very broad but attenuates in our atmosphere much faster. Many animals that can see a little into one spectrum or the other can see a little into both. UV runs from ~4,000 – 10 Angstroms

While visible light runs from ~7,000 to 4,000 Angstroms. Not much at all really we are some of the most limited animals when it comes to perception of light.

If you think about it like this a person with the power to perceive even ¼ or either of those two spectrums would literally be getting hundreds of times more information than a normal human. Something else to consider the measured spectrums of the EM field go all the way from Radio waves (>10,000,000,000 Angstroms to Gamma Rays <0.1 to 0.001 Angstroms) There are techniques used in major industry to gather tons of information on things just by being able to sense narrow bands of these spectrums.

PS: Things that are subject to the UV spectrum look much brighter and clearere when viewed under UV light not darker. I know this from years of experience working with Inspection equipment.

[PhilFleischmann]

So how do those nocturnal hunting animals like cats and owls see well enough at night to chase and catch prey? Is it UV, or greater light sensitivity, or both?

[Dust Raven]

So how do those nocturnal hunting animals like cats and owls see well enough at night to chase and catch prey? Is it UV, or greater light sensitivity, or both?

I don't think anyone can say for sure, but one fact that is known is that cats have a greater light sensitivity than humans. They can see well in the dark because their eyes can let in more light (it's that slit pupil thing), and adapt quick enough to a light change to avoid being blinded by a sudden shift in luminosity. Other nocturnal animals hunt/navigate through senses other than sight, relying on hearing and smell. Some have really good night vision though, for one reason or another.

[Bloodstone]

Several anatomical differences.

Eyes have two types of cells called photorecpetors. Cones are more responsive in bright light and give us our range of color vision. Rods are more responsive in low light and give us night vision. Cats and other nocturnal animals have more rods than cones.

In additon, most nocturnal animals have a membrane on the back of their eye that reflects light back onto the rods. It's known as a tapetum lucidum. This allows them to double the effective amount of light that the rods get exposed to. This is also why you can see animals eyes shining brightly in your headlights. The light is bouncing off the back of their eyes and reflecting back at you.

In addition, the way certain animals pupils are designed allows them to let more light in, thus maximizeng the rods exposure. To use a familiar example, in bright light a cats iris closes to make the pupil appear as a thin slit. In low light, the pupil is so large that the iris iappears only as a thing ring of color around it.

Cat's also have additional senses that help. For example, their wiskers detect vibrations and air currents. They are also the length of the cats shoulders, so they know based on how their wiskers feel wether the rest of their body will fit through a given space. Owls have amazing hearing and can detect a mouse or vole under several feet of snow from a considerable distance away.

[Guyon]

I was actually thinking of starting a thread about U.V vision.

For 10+ years, I've run a character with it in a Champs game with multiple GMs.

To this day, I've never been able to use it beyond sometimes being able to see in dark conditions.

How do other players use it in their games and what kind of techno-babble do they use to rationalize those uses ?


Funny you should bring that up. In our last game the heroes boarded an alien space ship. It seem to have no control markings, light panels, & had no read outs on the screens. After a while they figured out that they were all in the non visible spectrum of light.

[Yansuf]

So how do those nocturnal hunting animals like cats and owls see well enough at night to chase and catch prey? Is it UV, or greater light sensitivity, or both?

While the details of how nocturnal animals sense at night may not be completely known (or it may be, not my field) they do not do it by UV vision. There is less UV available at night than there is normal light, unless you have an artificial source.

[Yansuf]

Just a little note for you to think of on this topic.

Infrared: Does not pick up heat or cold or any thing like it. What Infrared does is allow detection a very broad spectrum of electromagnetic radiation emitted from the transfer or energy from one source to another. IR is incredibly useful in things like inspecting metals, structures and dark areas. As a structure with a flaw in it will have different impedance zones and the heat of things going through and near them will change IR radiation will be emitted. This means you can see very well in perfect darkness. I have done quite a bit of MSHA work (Mine Safety and Hazard Awareness). You will also be able to see little flaws. However there are limits to perception. As in if you are at a sensitivity (gain) level to be able to see flaws in structures and in caves then a source like fire (with tons of heat transfer to the air) will potentially blind you and damage your eyes (equipment). In our society we use IR technology for inspecting Electrical wiring, in the air, buried and behind walls. We also use it for looking at concrete pylons for fishers and breaks. IR runs from ~10,000,000 – 7,000 Angstroms


IR vision is defined as seeing heat, it is therefore equivalent to "thermal imagery" sensors.
Yes, very hot sources can blind such sensors, just like a bright light in your eyes can dazzle you. Flares are used to dazzle night vision gear, for example.

[input.jack]

.... most nocturnal animals have a membrane on the back of their eye that reflects light back onto the rods. It's known as a tapetum lucidum. This allows them to double the effective amount of light that the rods get exposed to. This is also why you can see animals eyes shining brightly in your headlights. The light is bouncing off the back of their eyes and reflecting back at you.

When I was working security at an apartment complex here in Oklahoma one night, I heard soemthing moving down in a culvert that ran behind the apartments.

Switching on my spiffy new mag-light, I shined it in the direction of the noise.

I caught a momentary glimpse of a cat looking my way, and then was STRUCK BLIND by the gleaming eyeshine. I swear, I was dazed for a second, there.

If Id had a flashlight that wasnt like daylight in a tube I might have stood a chance ;)

[Markdoc]

I caught a momentary glimpse of a cat looking my way, and then was STRUCK BLIND by the gleaming eyeshine. I swear, I was dazed for a second, there.

If Id had a flashlight that wasnt like daylight in a tube I might have stood a chance ;)

Think what it did to the cat: he got 8-16 times what you did :eek:

cheers, Mark

[McCoy]

In additon, most nocturnal animals have a membrane on the back of their eye that reflects light back onto the rods. It's known as a tapetum lucidum. This allows them to double the effective amount of light that the rods get exposed to. This is also why you can see animals eyes shining brightly in your headlights. The light is bouncing off the back of their eyes and reflecting back at you.
And some very rare humans. My college roommate had that. His eyes seemed to glow in low light. On the plus side, he never woke me by turning on the light in the middle of the night.

[Bloodstone]

Can you be certain he wasn't an alien scouting our world for galactic conquest?

Seriously, never heard of that before. I'll have to look into it.

[Lucius]

And some very rare humans. My college roommate had that. His eyes seemed to glow in low light. On the plus side, he never woke me by turning on the light in the middle of the night.

Did he major in Chemistry? I might have met this guy.

Lucius Alexander

He told me his father had limited vision into the UV spectrum too.

[McCoy]

Did he major in Chemistry? I might have met this guy.

Lucius Alexander

He told me his father had limited vision into the UV spectrum too.
Business Admistration IIRC.

[Dust Raven]

When I was working security at an apartment complex here in Oklahoma one night, I heard soemthing moving down in a culvert that ran behind the apartments.

Switching on my spiffy new mag-light, I shined it in the direction of the noise.

I caught a momentary glimpse of a cat looking my way, and then was STRUCK BLIND by the gleaming eyeshine. I swear, I was dazed for a second, there.

If Id had a flashlight that wasnt like daylight in a tube I might have stood a chance ;)

New slogan for Mag-Light: It's like daylight in a tube!


That reminds me of a D&D game where the mage of the group cast Contunual Light on the inside of a scroll case and ended up with a flashlight that turned off when the cap was put back on.

[Cancer]

The thing about the tapetum is that there is a price in acuity. Because the light gets to make two passes through the retina, there's an inevitable "double image" effect because you can't have both incident rays and reflected rays have the same focus. It's not a strong effect, but it is made worse under low-light wide-aperature conditions.

Humans (generally) have no tapetum and have better fine-scale resolving power in multiple colors under well-lit conditions. Our vision is optimized for a different environment and task than that of a night-hunting predator.

The pit vipers have thermal IR sensors that are ranged, but not imaging, detectors; they aren't part of the vision system.

[Barton]

FYI: UV is also some what effective in jungles or anywhere else large amounts of rotting biological material exists. Many bacteria give of UV light as part of normal metabolsim, so in jungles UV is useful. I read about this when UV was being experimented with in Vietnam.

[Dust Raven]

The thing about the tapetum is that there is a price in acuity. Because the light gets to make two passes through the retina, there's an inevitable "double image" effect because you can't have both incident rays and reflected rays have the same focus. It's not a strong effect, but it is made worse under low-light wide-aperature conditions.

This effectively makes such animals as cats nearsighted. That focus is great close up, but anything across the room is blurry. I'm not too certain how blurry, or how quickly vision drops off because of it.

[prestidigitator]

There is less UV available at night than there is normal light, unless you have an artificial source.
That is not necessarily true. While for any particular frequency or comparable frequency band there may be less intensity than there is for visible light, the UV band(s) is/are huge compared to the visible spectrum. To some of it the atmosphere is mostly opaque. To some it is reasonably transparent. I'm not sure about the total intensity of the entire UV spectrum compared to the visible one, but I'd be willing to bet it is at least as bright. Things in the real world really don't take advantage of the entire UV spectrum, but UV Vision in the gaming world possibly could.

[feralucce]

Are we discussing rules or science? cause scientifically speaking, at night, there is not enough uv radiation to see by (equip a video camera with a 2-14 nanometer pass through filter and you will see this)... if you have an ACTIVE uv source, then you could use teh same filter and get a picutre, but it is easier to use infrared LEDs and a 400-600 pass through... just my two cents...

[Rapier]

I can actually accept some UV vision.

Consider the stereotypical drow/dwarf/deep gnome. Living underground. There IS no natural light as we know it. No sunlight or starlight. It's pitch-freakin-black ALL-THE-TIME. UV light is actually a fairly common by-product of a number of natural phenomenon (sp?). Many fungi and molds produce it and its a natural by-product of decomp. In the deep-dark underground it is probably the ONLY source of natural light around.

I could very easily see (and here comes the cross-post part) dwarves and other underground races EVOLVING (GASP!) to the point that they were VERY, VERY sensitive to light in the UV range. This would allow them to at the very least see things that radiate in the UV spectra and at most use the UV spectra as a light source to pseudo-match our normal vision in the normal sight range of visible light.

Is it realistic? Is it natural as we know it? CMON! We are talking about a freakin game with fire shotting out of people's fingers and dragons and mermaids and **** for Aaron Allston's sake! SPELL IT!!! G-A-M-E!

[Frenchman]

I have to agree with Rapier above.
I like to have my game have some basis in 'real' science and the 'real' world (note the quote-unicorns, I'm willing to stretch this definition of 'real')
At the same time I'm not going to let a little thing like common sense get in the way of a little thing like a fantasy wizards spell, or a super's ability to regenerate from ashes, or anything else for that matter.
Sometimes something is in my games just because it looks/sounds/works better that way. I let characters with UV vision see in low-light conditions and grant a few other benefits because it works, dammit. And since UV vision sounds better than Nightvision "Darkvision" I let it work like those if it needs to.
After all, some sap just paid 5 character points for his UV vision. If someone else bought IR vision and yet another player bought Nightvision, I want them all to have distinct (if possibly overlapping) uses and purposes, all roughly comparable.
Then again, it is just a game.
I'm not going to get worked up over how someone else plays it, but I will listen in just in case theres an idea good enough to steal.

[Bloodstone]

I don't think anyone has actully saying "Don't use UV Vision in your games, man! It has no basis in reality!"

Somone asked why it works like that, several people answered it's a D&Dism, a few people offered up how the power could be changed to mirror reality a bit more closely and the conversation drifted form there.

I don't think UV vision as it's done if 5ER and many other games is very "realistic". And I don't care, 'cause it's neat ;)

[Markdoc]

And some very rare humans. My college roommate had that. His eyes seemed to glow in low light. On the plus side, he never woke me by turning on the light in the middle of the night.

All humans have this to some extent: we don't have a tapetum lucidum, but the human retinal structure does reflect incoming light to some extent - it's what gives you red-eye in flash photos.

Some humans have more of it than others - I do, for example. I've freaked several people out (including my own wife and the wife of one poster on these boards) because if you shine a bright light on my eyes in near darkness, you can get a flash of reflected light like shining a light on a cat's eyes.

I've never had anyone say my eyes glow in low light, though!

I also have unusually good night vision, but I am not sure if the two are related. Human eyes are not efficiently evolved to make use of rear-reflected light.

cheers, Mark

[Cancer]

There's also lots of tricks one can learn for making the most of your vision in low-light situations. I don't think my low-light vision is intrinsically particularly good, but I know lots of things about getting the most out of it. And yes, I also have scared several people with what I could make out in the dark.