Summary:
The Light Relay (LR) seal has a 4"-diameter detector spiral on the left and a 4"-diameter emitter spiral on the right. If the detector receives enough light of a specific color (chosen at infusion time) then the emitter sends out a constant amount of light of a specific color (chosen at infusion time).
Note: This seal is a complete pain in the ass for the QMs. There are a crapton of physics questions that can be asked and we have neither the background nor the spoons to deal with it. We've done our best to answer as many of them as we can and we are going to do our best to be consistent about applying those answers. That said, if we forget something and do it wrong or if we have to make a judgment call and it ends up being inconsistent then chakra be trollin', yo.
Details:
The blank for the Light Relay (LR) seal is 12" wide. It has one 4"-diameter spiral in its left third, a bunch of stuff in the middle, and another 4"-diameter spiral in the right third. The one on the left is the receiver and the one on the right is the emitter. Don't read too much into this as far as seal theory goes; we're only specifying the shape to make it easy to talk about. Please don't poke too hard at the relationships between shape and function.
Treat the detector spiral as being mostly equivalent to a real-world light sensor that only reacts to a particular color of light and has a threshold for activation. If that threshold is passed then the emitter spiral lights up.
At infusion time you choose what color the seal is sensitive to (e.g. 'leaf green') and what color it emits (e.g. 'robin-egg blue'). If a sufficient amount of light of the specified color strikes the receiver, the emitter will emit light of its specified color at the same intensity as a Harumitsu's Outstanding World-Saving (HOWS) seal.
Only the ink that forms the detector spiral absorbs light. The entirety of the detector spiral must be exposed. If you fold a corner over it or place a straw across it then it stops working. Chakra being chakra, the exact limits on this are fuzzy; a single speck of dust won't deactivate it, but a sufficiently heavy sprinkling of dust will. The seal does not need to be lying flat; you can fold it in half and it will still function. The emitter spiral does not have this restriction; it works like any normal light source in that if you block part of it then the light from that part is blocked but the light source does not shut down.
Chakra being the troll that it is, close investigation of how much light is enough to activate an LR yields inconsistent results. (i.e., the QMs refuse to get too deep in the physics weeds and will use their best judgment.) As general benchmarks:
- Jiraiya's Awesome Daybright Lantern seal is roughly 900 lumens
- Haru's Outstanding World-Saving seal is roughly 300 lumens, which we are treating as bright enough to comfortably read by at arm's length at night under a clear sky (i.e., not daylight but not pitch black)
- HOWS is sufficient to activate an LR at 3 meters. Because we don't want to mess around with this, we'll assume that it's sufficient to activate an LR at 3m during daylight or at night. It might not be sufficient if the area is exceedingly bright, exceedingly smoky, etc.
- To find out the activation range of any light-producing seal for LR, take the distance from which you can comfortably read by the seal in question and multiply by three.
- Again, the QMs do not have the spoons to faff around with physics on this. We'll do our best to be consistent but if we have to make a judgment call and it ends up being inconsistent then chakra be trollin' yo.
The receivers are roughly as sensitive to color as the human eye and they will only activate for the color that was chosen at infusion time. Using
this color list for reference, if you set it to detect "Amber (SAE/ECE)" (#ff7e00) then it will not activate for "Blood Red" (#f35336). At the same time, it's not completely precise, so at least some of the time it will activate for "American Orange" (#ff8b00).
Fortunately, the color emitted by an LR is stable, so if you have an LR seal set to emit American Orange then it will always activate another LR that is set to detect American Orange.
Q: Can you verbally describe a color to another sealmaster such that they can accurately create an LR that detects and/or emits that color?
A: No, but if they see the color then they can do it. (NB: There might be some exceptions if people have color blindness or other conditions that distort their color perception.)
Q: Can a sealmaster reliably reproduce a color that they used in the past?
A: Yes.
Q: What direction(s) do the seals emit in?
A: The same sort of hemisphere that you would get from the top face of a glowing-hot flat piece of metal. (The seals are heatless unless specified otherwise; we are only referencing direction here.)
Q: What is a distance that something in the way of the seal will reliably not block functioning? An inch?
A: Sure, why not. If something is 1" from an LR then it can be discounted for purposes of whether or not the seal works. Again, chakra be troll and inconsistent yo.
Q: Do transparent materials (like a perfect glass or water) blocking the spirals prevent activation?
A: If you have sufficiently clear and flawless glass (i.e., sufficient for eyeglasses) then no, it does not block activation. The Aburame are among the very, very few people in the setting capable of making glass of this quality, and only in small amounts. There is no practical way to safely put a seal underwater to test if that would be an issue.
Q: What happens if you shine light parallel to the seal paper? So light is touching the absorption spiral but moves across instead of into it.
A: The same thing that would happen with a real-world light detector, to the limits of the QM's understanding, memory, blah blah blah.
Q: If you write the seal on transparent paper and you shine light from behind the absorption spiral. What happens?
A: There is no such thing as transparent paper in the setting, nor would Hazō be willing to scribe a seal on glass.