# An "I'm a writer who doesn't know squat about lighting" question.



## speters33w (Jan 12, 2020)

This is an "I'm a writer who doesn't know squat about lighting" question.

I thought about putting this question in the caving forum, but maybe here is better.

My wife and I are buttoning up the final stages of a book we are writing together.

The scenario is an interstellar ark sleeper ship, a young woman is unfrozen and finds herself alone on the ship. The book is a transcription of her recorded diaries.

Do the lighting measurements in the editor's note below make sense? Or even the units of measurement? If not, what would make sense?

The corridors in the spaceship are supposed to be lighted just enough to barely see a wall 2.5 meters away, but not 4 meters. "OENA" is supposed to mean "Old Earth North American" measurements. Used for Imperial (UK "Old Money") measurements, inches and feet.

This is the Audio Diary of Anna Smith, Deckhand Second Class on the UESS Volery.

It’s … uh … 6 hours and 10 minutes since I started the run timer. And I’m back from reconnaissance. Let me tell you what I found.

[Pause]

It’s dim out there.

I suppose that there wasn’t much reason to have the lights on full power while everybody was frozen solid, and I should be glad there’s even a dim light. The droids probably need just a little visual input for their sensors.
It’s light enough for me to make my way down the passages and corridors, but it’s spooky to walk in semi-darkness.
You can’t see much.

What are the side corridors? Like ten feet wide? You can just see from one side to the other in them. The main corridors — I don’t know how wide they are, maybe double that? You can lean against the wall on one side, and the other side is lost in darkness.

*[Editor’s note: Main corridors were 4 meters wide, approximately 13 OENA feet. Side corridors were 2.5 meters, approximately 8 OENA feet. During hibernation phase, all corridors were illuminated at one side only to approximately 100 µlx, or 0.0001 lumens per square meter. Human perception would have seen the corridors as wider than they were in reality.]*

I haven’t seen any people, dead or alive.

I haven’t seen any droids, either.​
Thank you in advance.


----------



## Modernflame (Jan 12, 2020)

There are far brighter lights on this forum than I, but I'll get the conversation started by providing a little context. The amount of light on the ground during a clear, full moon lit night is about 0.25 lux. Dark adapted eyes will have an easy time navigating under these conditions. Since the human eye does not perceive brightness in a linear fashion, it takes about four times as much light to appear twice as bright, or four times less to appear half as bright. So 0.0625 lux would appear roughly half as bright as full moonlight. Divided by four again, that's still 0.016 lux. The next iteration would be 0.004, then 0.001. You'd have to go two more steps to get somewhat close to your micro lux measurement. One could argue that hibernation would put the human eye into a deep state of dark adaptation, but 100 μlx is a very, very small amount of light. 


Perhaps someone with a lux meter can contribute to the discussion. A flashlight producing one lumen, or even sub lumen output and then pointed at the ceiling provides more than enough diffuse illumination to navigate indoors. Assuming the light is evenly distrubuted, approximately how much light is on any given surface?


----------



## parametrek (Jan 13, 2020)

> The corridors in the spaceship are supposed to be lighted just enough to barely see a wall 2.5 meters away, but not 4 meters.



It sounds like your character isn't carrying a light but the light fixtures are running dimly?

In that case the situation you describe isn't possible. Dimming the lights will not cause you to only be able to see a certain distance. Instead as the overall illumination lowers you see less clearly. Think getting progressively worse eyesight. Reading signs and stuff would get harder and you'd need to be closer to them.

But there is no change to how far you can see. Go outside in the dark when the moon is at various phases. When the moon is full you can see miles away to the horizon. When the moon is a sliver you can still see miles away to the horizon. Visual acuity will be less though. Under a full moon you might easily be able to tell what people are carrying at 100 meters. Under a crescent moon you might only be able to count how many people there are.

Or try wearing sunglasses indoors. Everything gets harder to see but there isn't some line past which you can't see.


----------



## speters33w (Jan 13, 2020)

parametrek said:


> It sounds like your character isn't carrying a light but the light fixtures are running dimly?
> 
> In that case the situation you describe isn't possible. Dimming the lights will not cause you to only be able to see a certain distance. Instead as the overall illumination lowers you see less clearly. Think getting progressively worse eyesight. Reading signs and stuff would get harder and you'd need to be closer to them.
> 
> But there is no change to how far you can see.



Thank you! So, from the "bright" lighted side she may not be able to perceive detail on the "dark" far wall, and from the far wall she would be able to see the details on bright wall always.

This is what I needed. So I will just leave the chunk of the "editor's" note that tells dimensions alone, and cut out the chunk with lumens altogether. We are using the "editor's" notes in case people in Canada love the story and people in the US don't buy it, because all the measurements are imperial.

The audio (that does not include the editor's notes) is already recorded, so we'll probably leave this sentence alone (since it's believable,) unless the publisher catches it.
What are the side corridors? Like ten feet wide? You can just see from one side to the other in them. The main corridors … I don’t know how wide they are, maybe double that? You can lean against the wall on one side, and the other side is lost in darkness. ​
I'm guessing there are very few people like yourself who will notice the problem. And, really, we will be thrilled to get a "correction" e-mail from a reader if someone is reading (or listening) to it with enough attention to detail to notice.

Again, Thank you!


----------



## Ken_McE (Jan 13, 2020)

speters33w said:


> This is an "I'm a writer who doesn't know squat about lighting" question.



Not to worry. You build it, we'll light it. We can light anything.

Been thinking about *parametrek*s concerns. They're valid. Got a potential way around the problem. You want her to be able to see (barely) but not see the far side of the corridor. Try this:

You have a line of emergency lights running down the middle of each corridor. They're not meant to provide seamless operations during lighting failures. They're meant to make it possible for crew to move around if something happens to the regular light.

Why are the lights left running when nobody is there to use them? Why waste electricity? These lights don't use electricity. They can't be turned off. They just run till they die.

The highest quality emergency lights of our day are gaseous tritium light sources, also called beta lights or trits. There are little ones sold here for flashlights. Your ship has big ones running in lines down the corridors. Trits contain radioactive gas. The ship designers had very bad attitudes about the possibility of radioactive gas getting mixed into their air handlers, so they are all recessed up into the ceiling behind thick layers of high strength glass to protect them from being smacked against when something gets carried by.

Because they are slightly recessed they shine on the center of the corridor, where you need to walk, but not either wall. They didn't need to light the walls. Even if light bounced off the floor and lit the walls dimly when they were new, they are no longer new.

Tritium has a twelve year half life, so a trit looses half its brightness every twelve years. By the time our heroine wakes up they're almost useless. Assume they get replaced for every trip, heck if the ship is reusable at all it probably needs a full rebuild in dry dock at every stop. If multiples of twelve don't work out, other gases can be used - any beta emitter will do. The other gases are not used much terrestrially because they are more dangerous than Tritium. For a star ship they could use something with a longer half life if they felt it was neccesary.

( https://en.wikipedia.org/wiki/Tritium_radioluminescence )

Don't know anything about your ship or your writing style, but the above is all hard science so you should be able to adapt it into pretty much anything.


----------



## aginthelaw (Jan 13, 2020)

I’m a lighter that doesn’t know squat about writing! Can everyone in the thread get a copy of the book? Marvel comics was great at incorporating science into their stories. Robert A Heinlein, issac asimov the same. Looking forward to seeing more of you


----------



## Ken_McE (Jan 14, 2020)

aginthelaw said:


> Can everyone in the thread get a copy of the book?



Depends if he leaves us a link.


----------

