UV vision

[Yansuf]

Re: UV vision

 

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

 

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]

Re: UV vision

 

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]

Re: UV vision

 

.... 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]

Re: UV vision

 

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

 

cheers, Mark

[McCoy]

Re: UV vision

 

In additon' date=' 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. [/quote']

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]

Re: UV vision

 

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]

Re: UV vision

 

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

 

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]

Re: UV vision

 

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]

Re: UV vision

 

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]

Re: UV vision

 

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]

Re: UV vision

 

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]

Re: UV vision

 

The thing about the tapetum is that there is a price in acuity. Because the light gets to make two passes through the retina' date=' 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. [/quote']

 

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]

Re: UV vision

 

There is less UV available at night than there is normal light' date=' unless you have an artificial source.[/quote']

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]

Re: UV vision

 

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]

Re: UV vision

 

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]

Re: UV vision

 

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]

Re: UV vision

 

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]

Re: UV vision

 

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

 

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]

Re: UV vision

 

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.