Sunrods kind of tick me off. Sure, I’ve heard the arguments; basically, is “light” important in your game? But 20 squares? 100 ft? Really? I started wondering, how many lumens is that? The answer is, as science always is, complex.
I’m by no means a math or science wizard, if any of my research nets false results, feel free to let me know. This is my first delve into all this.
The first thing I had to learn was the terminology. I found a decent article that does a good job of putting this all into lamens terms.
- A lumen is how bright a lit object is, one foot from the source of light.
- A footcandle (U.S. term) is how bright the light is, one foot from the light.
- A lux, or illuminance, is how bright the room gets because of the light.
Ok, we know a sunrod sheds “bright light out to twenty squares.” So now, we have to define “bright light”. This brings us into the science of the humans eyes reaction to light.
- Photopic vision is how well the human eye can see in well-lit conditions.
- Scotopic vision is how well the human eye can see in dim-light (darkness).
- Mesopic vision is the combination of the two.
Further breakdown reveals that photopic vision “sees” in a cone like fashion at great detail and color perception; while scotopic vision “sees” wavelengths of light solely with the rods of our eyes yielding a severe loss of detail and color discrimination. Mesopic is the combination of the two, it “sees” with both the cone and the rod,
This is all from wiki of course, I came across an interesting tidbit under scotopic vision, “In other species, such as the Elephant Hawk-moth (Deilephila elpenor), advanced color discrimination is displayed.” In my opinion, this is clearly darkvision, proving that darkvison can see colors and allows us to do a perfect breakdown, into D&D terms.
- Photopic = Bright Light – Detail and color
- Mesopic = Dim Light – Loss of detail and color
- Scotopic = Darkness – No detail, no color
Now, back to the sunrod. We now know, in scientific terms, it produces photopic vision one hundred feet from it’s source, but there are varying degrees of photopic vision.
This is where I have to get into math, and like I said, not my strong suit. Feel free to help me out here.
A flux of 1000 lumens, concentrated into an area of one square metre, lights up that square metre with an illuminance of 1000 lux. The same 1000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux.
metre = 3.2808399 ft
square meter = 10.763911 square feet
ten square meters = 107.6 ft (at ~ 100 lux).
One footcandle ≈ 10.764 lux.
So the twentieth square is (approximately) ten footcandles, and ten foot candles is equal to 107.6391 lux.
I found a nice relationship chart here…
- Full daylight is about 10,000 lux
- A cloudy day is about 1000 lux
- A lit parking lot at night is about 10 lux
- A full moon is about 0.1 Lux.
This gives us something we can envision…. but remember that part from before, the same 1000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux.
That’s a ratio of about 1 to 10. We can easily work backwards from there to determine that the sunrod itself is 1000 footcandles (the same as an overcast day).
1000 footcandles = 10,763.91 lux (full daylight). That’s bright! Real bright!
What does that mean for the person holding a sunrod? Can anyone see past them? Can anyone even see them at all, or are they just a ball of brilliant light? Not to mention the effect this would have on the scotopic eye.
Check this out. It’s a tactical flashlight that produces 60 lumens, supposedly “enough to temporarily blind and disorient a person by impairing his night-adapted vision.” Remember a lumen is how bright a lit object is, as opposed to how bright the light itself is (foot candle), but the two measurement are about the same, just two sides of the same coin. So 60 footcandles is “enough to temporarily blind and disorient a person by impairing his night-adapted vision.”
What does 1000 foot candles do?
— Revision —
That’s it for now, I’m tired.
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