# Range of Illumination



## skip.knox (Mar 2, 2019)

OK, here's one for the Presently Assembled.

Your party is trudging through tunnels and caverns. You can give them any sort of pre-19thc lighting device--lamp, lantern, torch. The question of the day is this: how far can they see?

I have found tons of articles on lumens and such. Not much use there. I found an article about from how far away a candle could be seen, but that's in reverse direction (still, useful information if you're moving your characters through enemy territory at night). I found plenty on how to make a torch, a lamp, etc. But in all these, not a peep about how much would be illuminated. There was one article from the Fifth Edition AD&D that posited a campfire could illuminate to a radius of eighty feet. The poster said maybe half that being well-lit. No word on how big a campfire, and anyway we aren't going to be carrying whole campfires at the end of a stick.

Movies are useless here. I'm guessing, though, that folks round here have some direct experience with this. The point of relevance for me is knowing how far I can have a character move away from the path before losing sight of it--iow, seeing a non-lit, non-reflective object using a torch or whatever. I'm guessing it's only a few yards, not hundreds of yards.


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## TheKillerBs (Mar 2, 2019)

If I'm understanding your question correctly, in candlelight you can still see outlines of furniture from about 12 yards away, assuming you have a direct line from the candle to the pieces of furniture in question. I remember my grandma had a gas lamp when I was a child and it illuminated about half again as well as candlelight, so perhaps you could see outlines  from about 18 yards away, again, assuming you have a direct line. Anything in shadow would still be pitch-black though.


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## skip.knox (Mar 2, 2019)

Thanks for that. Twelve yards makes for a pretty big room. You sure about those distances? Sorry, I don't mean to challenge; just checking.

Objects would definitely be lost in shadows. Another point about seeing in the dark is how the eyes adjust to light, so looking away (say, from the campfire) would make a person more blind than usual, until the eyes could adjust to the darkness. Couple that with the shadows, and the fact that the party is moving, which means the light sources are moving, and you have lots of opportunity both for hiding and for seeing things that aren't there.

Back to your gradma's house. A torch might throw more light, since the source is larger. A lamp probably would not, since there we're talking about a wick much as with a candle. Putting a polished surface behind the source could improve matters.

I look forward to hearing from others on this. Another point of relevance for me is where my characters enter a large cavern. How big does it need to be such that we cannot see the ceiling or the far side? Similarly, peering into a chasm; how far down?


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## TheKillerBs (Mar 2, 2019)

It's a corridor, not a room. It has four 3x3 m rooms on one side. Given the placement of the table stool thingy and where I was at the time, it'd be a little less than that.

Re: the gass lamp. I don't particularly remember the particulars, but it looked like the dead flame lamp in wikipedia's article on kerosene lamps. That same article states that oil lamps start their lighting outputs from about 50 lumens, compared to 13 lumens for common parafin candles, for whatever that's worth. I don't know how that would translate into perception even if it were true. I stand by what I said about half again as much, though.


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## skip.knox (Mar 2, 2019)

Got it. That's helpful.


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## CupofJoe (Mar 3, 2019)

I'd say it depends on the walls of the tunnel. I've walked slate mines with dark grey walls and we used tea lights to mark our way. They don't light up very much at all when the walls are dry and the lights at floor level. But add water seeping down a wall and you can suddenly see something fifty yards or more away as the water flickers and reflects. The light the tea lights cast [or the flickering of the shadows more accurately] can be seen for a very long way. I don't know how far but at least fifty yards.


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## skip.knox (Mar 3, 2019)

OTOH, light going into a large cavern might not light up the farther wall at all. Hundred yard caverns are not all that rare. It's difficult, these days, to find a cave system where they'll let you bring along an oil lantern for research purposes.


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## Malik (Mar 3, 2019)

Something you learn the hard way is that moving by torchlight sucks because one quick glance at the flame to see how it's doing and your night vision is shot to hell, which even once the afterimages clear involves a loss of granular detail at the edge of your illumination. Tough habit to get out of, BTW. You get worried about how long the torch will last, and then you look at the flame, and then you're blinking hot pink gummy worms everywhere you look, and once those clear you have zero distance vision for a while, so you wait for that to clear, and then it's been a few minutes so you wonder how the torch is holding up, and around and around.

An experienced adventurer will know this, but your "farm boy"/"lost prince" trope (or, in my books, a guy from Earth making his way by torchlight) might not. It gets really frustrating.


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## skip.knox (Mar 3, 2019)

Ayup. Read about that in one of the articles; made instant sense. I recall being at campfires and you stare into them because ... well, fire ... and then you look up and can't see a ding dang thing. Ya gotta tell the sentry "don't look at the fire, you idjit!"

I figure the same will apply to whatever is the source, whether lamp or lantern or torch. Might work it in for a bit of comic relief.

Still trying, though, to get a general idea of how big I have to make a cavern, or how large to make a formation, before it fades into the shadows of a cavern. I don't need to be precise, but I do need to be in the neighborhood. Are those dwarf-built towers four stories high before you can't see the top, or forty stories? Verisimilitude, I do love you, but sometimes you're a peck of work.


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## CupofJoe (Mar 4, 2019)

One thing I'd add... In a cave with no lighting, there is no amount of "night adaptation" that will kick in and let you see. 
After about 15-20 minutes in an unlit mine, you do notice that you can see the glow of  luminous dial on a watch, through a waterproof gore tex top. 
You can also see colours and shapes but I'm fairly sure that is your brain turning the gain all the way up to eleven [trying to see something] and the rest of your mind trying to decode the noise of Nothing into something it can cope with and understand. Lots of Paisley patterns and fractals...
And if you are ever in the position to try I highly recommend sitting in utter darkness for a while to let you mind unspool.


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## Sheilawisz (Mar 4, 2019)

Well I have no experience with cavern exploration, but I have spent some extremely dark nights camping in the forest. It's true that even a strong campfire provides only a modest circle of warmth and light, with nothing but cold and darkness beyond.

People that have never experienced night in rural areas are sometimes surprised at how dark and frightening it can get. There were a lot of fears and superstition regarding night in the days before electric lights, and it would be great if more Fantasy stories described in detail what the old night used to be like.

About the cavern: Illumination from lanterns and torches would be useful for a distance of a few meters only, a high ceiling would be invisible and it would be extremely easy to get lost.

I would not give any precise numbers in a story, just a few descriptions should be enough to provide a feeling of how unnerving the experience of cavern darkness could be.


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## Insolent Lad (Mar 4, 2019)

I should have paid more attention when I was without power for two weeks after Hurricane Michael. I was walking around the house quite a bit by candle light.


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## skip.knox (Mar 4, 2019)

I agree with Sheilawicz that I do not need exact numbers. It's more a case of this: if the character cannot see the far side of a cavern, do they strike out straight across or do they move along the walls? When they encounter a dwarf city, how tall is a building before it's lost in the darkness? 

These directly affect how long it would take to explore a building, or to get across a cavern. Or, equally important, whether they could see to the bottom of that cavern (can always lower a lantern, of course).

Thanks for all the replies. It struck me as odd that this information was not more readily available on the Net.


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## Sheilawisz (Mar 4, 2019)

skip.knox said:


> It's more a case of this: if the character cannot see the far side of a cavern, do they strike out straight across or do they move along the walls? When they encounter a dwarf city, how tall is a building before it's lost in the darkness?



I think it's more logical to assume that most characters would choose to navigate a dark and unknown cavern by moving along the walls, or at least that's what I would do myself in that situation. The magical solution would be to have torches or crystals capable of projecting beams of light just like one of those powerful LED flashlights, or to release many sparks or flames that fly everywhere and lit the place up.

About the building in a city... Well, it would be much easier to describe a tall structure as completely visible if it happens to be a Full Moon night. Otherwise, most of it would be invisible in the darkness unless its material or the windows can be effective at reflecting light emitted by street lamps, campfires or something else in the city below.

What if there are lamps inside of the building, so the windows glow and you can easily see them from the streets?


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## skip.knox (Mar 5, 2019)

Good points, but we're going to the center of the earth, so going along the walls isn't always possible. It's more about how to describe a space when first entering. Can the further wall be seen? If it can't, what does that imply about the size?

I do indeed have some crystals in the walls, same as Verne did. I could magically light up most any space, but shadows lend mystery. 

Good suggestions here, folks; I do appreciate it. But don't you find it curious that the answer isn't simple and readily available? It's a reflection of modern living, I suppose. I think I may head over to some caving forums and do a search. They'll be using modern lights, of course, but I bet the question's come up.


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## pmmg (Mar 5, 2019)

Having recently been in a cave, I would add that if moving in the dark, it takes only one stalactite to show the folly of thinking one can feel their way around. Those things have no give, and one at head level will make itself known.

I would think another thing that would become common from too much darkness is that your eyes will play tricks on you, and you might come to think the place is haunted.

I saw that you mention D&D dragons rules for a fire. Generally, I find the RPG aids do try to make a good effort at judging things like that right. When I used to play, I think it was a torch could illuminate 60'. That would likely be very well lit in about 10' and getting dimmer further out. If someone's eyes were well trained, I suspect they might be able to make out dim details further out as light tends to reflect back, so a lone stalagmite might have a type of outline a bit further out, but you would have to really look for it.

If the cave wanderer's had a way of focusing the light and directing it, I would suspect the range could be increased in one direction. Say 100', assuming it was torch light and not these new LED flashlights. In the cave I was in, we had a tin bucket, with a hole in one side someone had pushed a candle through. It was crude, but it did direct the light. Hard to tell the distance though cause the cave had its own lighting in most areas.

Here is a picture of light we had, though the lighting in the picture comes from something else.


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## skip.knox (Mar 5, 2019)

All good points, pmmg. I do have a dwarf in the company and can use him to "see" things others cannot. At the same time, I have utter novices and can use them for eyes playing tricks.

I've already joined a caving forum to ask my question, but one thing I spotted in reading their forums that hadn't occurred to me: with certain lights, you might have good light forward, but if it's a focused beam you can't see your own feet! That might be the case with certain lanterns, e.g.


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## MrBrightsider (Mar 8, 2019)

I actually remembered this thread driving through a military base the other night.

I was visiting a buddy, driving home around 10pm, and it was pitch dark. Raining, so it was cloudy. No lights since it's in the middle of nowhere. It was so dark that even with _car headlights _I couldn't see more than ~20 feet in front of me. And to the sides? No dice. I can't even imagine what it would be like in a fantasy setting, trudging through the wilderness with nothing but a lantern or a torch. A guy in a black cloak could be following your party no problem at a distance close enough to hear conversation. I was honestly surprised how dark that dark could be.

Gives me new respect for how close something like a damn Jaguar could get to you before you could see it--probably pouncing distance no problem.


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## skip.knox (Mar 8, 2019)

Especially if it was a Jaguar XKE!  ;-)

Thanks for the post. It's sort of surprising how much work it would take to re-create a fairly ordinary historical or pre-modern scene like trekking at night. I have a vivid memory of being with a group of friends when we thought it would be fun to go into Forest Hills Park in Portland Oregon. At night. Now, that park is several miles long and a mile or more wide, completely undeveloped (or was way back in 1970), but it's actually inside the city limits. So we were walking on a lit street (we, too, were somewhat lit), then you can spot a path and plunge right into heavy Northwest forest. It's huge fun in daylight.

At night, it was terrifying. So much so that we turned back within minutes, which was unwittingly smart as the hills are steep and there's plenty of things to fall over or into. And, bonus points, none of us had a flashlight or any other illumination. I got a brief taste of the origin of those scary night monsters of medieval tales. You start seeing things *real* fast.


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## Malik (Mar 8, 2019)

MrBrightsider said:


> Gives me new respect for how close something like a damn Jaguar could get to you before you could see it--probably pouncing distance no problem.



So no shit, there I was . . .

I was visiting a wildlife park some years ago with my nephew, and I remember walking along the fence by the mountain lion pen, and the mountain lion pacing alongside us through the underbrush not ten feet away. It was just hanging out, following us with interest. Damn thing was almost as big as I was, and completely silent even though it wasn't remotely trying to hide. It kind of slides along, weightless on these huge footpads. It was raining a little bit, as it does around here, and even the sound of leaves under its feet sounded no different from the raindrops. I have no doubt that if it didn't want you to know it was there, it could stalk and kill you in broad daylight.

"Clever girl."


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## MrBrightsider (Mar 9, 2019)

And can you imagine? That was every day life for that time period. No wonder they made up stories about all sorts of terrible things that lurk outside their little village. Like half the stuff out there wants to eat you.


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## skip.knox (Mar 9, 2019)

It's a commonplace to say medieval peasants lived most of their lives within fifteen miles of their home village. That's not an arbitrary number. It's the extreme limit of how far you can get and still get back home before nightfall. It's not only the dangerous things that prowl in or near the night (lots of predators out around dusk, and you sure don't want to stumble over a sleeping boar), it's also that it's far easier to get lost, you now have to bring food and camp gear, and some sort of weapon. It's a whole different proposition to travel multiple days.


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## MrBrightsider (Mar 11, 2019)

That paragraph right there could be an entire novel. Who would have thought "Peasant gets lost in the dark" could be so compelling?

The first ever serf psychological horror story, hah.


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## Mark Huntley-James (Mar 24, 2019)

From practical experience with candles and the like, air currents are a menace. The moment the flame starts flickering, shadows move and whatever you thought you could see has changed.  Back when I did seventeenth century battle enactments, one of the period pieces some people had was a pierced candle lantern - basically a metal can with holes poked in the walls to let some light out. It's not as bright as the bare candle, but it controls the air currents and provided there are no holes in the top of the can, you don't trash your night vision when you glance down.


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## skip.knox (Mar 24, 2019)

Mark Huntley-James, do you recall roughly how far you could see with that shielded lantern? It's surprisingly difficult to find estimates.


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## Mark Huntley-James (Mar 24, 2019)

skip.knox said:


> Mark Huntley-James, do you recall roughly how far you could see with that shielded lantern? It's surprisingly difficult to find estimates.



Sorry, no.  It was 10+ years back and I never saw one in use where there was no other illumination. They mostly came out around the camp fire of an evening and we never owned one ourselves. In the privacy of our own tent we used that traditional seventeenth century lighting system - the propane gas lantern.

My suspicion is that range would be very dependent on the number, size and distribution of the holes. Some of the folks who played officers had very fancy ones with the holes cut in intricate patterns - no better for the light, but it looked very fine when lit!


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## skip.knox (Mar 24, 2019)

Yeah, I'm going to have to go with what is story-convenient, I think. My characters are in deep, lightless caverns, using Ruhmkorff lanterns--Jules Verne made use of them--so they'll have some sort of container plus a backing mirror. Since my devices are powered by phlogiston, I can probably have it reach just exactly as far as needed and not an inch farther. I was just looking for context, but also whether a person might see a ceiling if it were a hundred feet overhead, or a thousand. I've already thought of adding some sort of reflective mineral or gem and so make stars at the center of the earth. Still not sure I'll use that, but sparklies are always fun.


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## Mark Huntley-James (Mar 24, 2019)

skip.knox said:


> Yeah, I'm going to have to go with what is story-convenient, I think. My characters are in deep, lightless caverns, using Ruhmkorff lanterns--Jules Verne made use of them--so they'll have some sort of container plus a backing mirror. Since my devices are powered by phlogiston, I can probably have it reach just exactly as far as needed and not an inch farther. I was just looking for context, but also whether a person might see a ceiling if it were a hundred feet overhead, or a thousand. I've already thought of adding some sort of reflective mineral or gem and so make stars at the center of the earth. Still not sure I'll use that, but sparklies are always fun.



That was a new one on me and I had to go and look it up!  I've actually seen a Ruhmkorff coil in action (moderately noisy as I recall), generating a 3-4 inch arc in air, and then when a wad of paper was  placed in the way the arc went around until it finally punched through the paper.


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