You may have completely misunderstood what I said.
Everything in the room is affected by the light, but the magus stays dark since no light reaches him. He sees the room normally but if he looks at his hand he only sees a dark shadow that hides the background.
IOW, CrIg and PM work backward of what was said: the magus sees everything but everyone see the magus as a dark shadow.
Nah I understood. If you read further.
I don't think magical lights should be default MR detectors. Never mind figuring out the lighting effects multiple lights with varying penetrations would cast on an assortment of individuals all with different MRs.
Ok, sorry. Yeah, if it was an MR detector it'd be an Aegis detector too.
Looks like Parma allows to feel but not to hurt. Shades of intelligent parma but I guess that kind is ok.
OK, then, the same question with an Aegis. Or how about a similar situation for flavor? During a pitch black night a dragon breathes flame upon the guards by the guardhouse outside a strong (meaning the flame wouldn't penetrate) Aegis. No one inside the Aegis sees the flame. Yes?
I just don't think it's so cut-and-dried. Natural effects of magical things are not supposed to be dispelled/resisted. For instance, you can't dispel a wound caused by a magical weapon. Even more extreme is the corpse of a magically created creature fed mundane food. So while I can see how the rules can be interpreted with the light not leaving the circle, I can also see it the other way. For example, heating an object placed within a fire is a natural effect, and so an object placed in the fire will still be hot when removed from the circle. Another natural effect of fires is to light their surroundings. I just don't see how this interpretation is invalid.
Chris
All this reminds me:
I use CrHe to create a torch, D: Sun.
The torch is lit on fire, is the emitted light magical?
I'd have to reread the Aegis description (and your excellent post on all the issues it involves), and the Dragon's breath would have to be "magical" (rather than "natural" as the result of a Creo ritual), and the night would really have to be so unnaturally pitch black that the grogs see absolutely nothing at all outside or inside of the Aegis (this means the Covenant too is total, pitch black darkness)... but yes, I guess in that case no one would see the flame. So?
As I mentioned in my first post, I think the question is whether a fire can produce "indirect light" in the same way that it can produce "indirect heat": an item magically heated emits non-magical heat, but does an item magically illuminated emit non-magical illumination? I'd say no, because if you heat a room with a fire, and douse the fire, the room remains warm without the fire (at least for a while) -- but if you illuminate a room with a fire, and douse the fire, the room falls dark as soon as the fire goes out. But as in my first post on this thread, I agree that there is margin for debate -- I just think there's more evidence for an interpretation opposite to yours.
Perhaps this could be adjusted a little bit. One guard stands inside aegis, speaking with another guard who is outside aegis. Hostile magus walks by and casts BOAF on the unfortunate guard outside Aegis, but with low enough level that it does not penetrage the Aegis.
What in your view, guard standing inside the Aegis will see?
Or if we think of the species... If species of light/item are magical... Woudl then species coming from magical animals be magical as well?
So would you agree to piece of metal being heated to point of glowing white (magically) to release light outside the circle?
If there is even the tiniest bit a ambient light, he'll see everything. After all, species of fire carry remarkably well even with little ambient light, as anyone who has seen a faraway fire in a moonless light can attest.
The question becomes tricky only if there is absolutely no ambient light at all. No moon, no stars, no torches, no fires in the distance, and absolutely no illumination at all in the Covenant. The grogs are out there standing guard blind as bats, relying presumably only on hearing and smell to notice stuff. Then, if the hostile magus arrives and tosses a BoAF at the grog foolishly standing outside the Aegis, the grog inside will not see the BoAF flying. He will suddenly see his comrade in flames (natural flames ignited by the BoAF). I have no problems with this. Do you?
No, magical stuff emits natural species. The issue is that species need light to travel -- they can't travel in pitch black darkness. So if the only source of ambient light is magical, and it's magically kept outside a certain area (e.g. by an Aegis covering the area), species will not be able to travel within that area.
As an example, Noctis was a faerie region completely inimical to light. Every source of light was instantly destroyed by the nature of the region. Its inhabitants had sight, but they could not use it because all they would see was pitch black darkness. This lasted until the Shining Knight retrieved DawnBringer, which alone defies the unnatural darkness of Noctis and now illuminates the whole regio in a shining, golden magical light. The magi have set up their covenant in Noctis, but because DawnBringer cannot penetrate their Aegis, within the Aegis all is dark. Moreover, anyone residing within the Aegis sees pitch black darkness even when looking outside, because species from the outside are carried by the magical light of DawnBringer, and that light is blocked by the Aegis. Not surprisingly, the inhabitants of Noctis assume that the magi are agents of Darkness...
Yes, just as a non-magical torch ignited by a magical spark illuminates and heats with a non-magical fire (I'm assuming your piece of metal is non-magical).
While the idea of light being the transport medium of visual species is interesting, it kinda break down when looking at a full moon through darkened rooms. I prefer the idea that light is the trigger that makes object emit species. Not that I have any clue which one is supported by Mythic Europe's beliefs.
IIRC, you don't see objects hidden behind others because the species are overwritten, which explain transparency.
It does not: that the room is "darkened" means that there is less ambient light, not that there is no ambient light -- after all, the moon's own light gets in, right? That's why I was saying that the example of the night so dark that you don't even see the BoAF within the Aegis would require extremely unusual circumstances. Unless you are in a sealed room/container, or in extraordinary environments, there is always some ambient light, even on a dark moonless cloudy night.
HoH:S explicitly supports the version "light is the medium through which visual species travel".
IIRC, you don't see objects hidden behind others because the species are overwritten, which explain transparency.
[/quote]
Both, actually. The problem is that you are thinking of light just like regular species, when it isn't. When discussing the mechanisms of sight and species, the philosopher always considers light and species separately, although they are related concepts. Species cannot transmit through darkness, therefore you need light to see species. However, you can see a light through darkness (that campfire on the hillside, or the moon), so when you see a light in the dark you cannot be seeing its species. There must be a qualitative difference here between light-producing objects and light-dependent species.
The Aristotlean view was that light came in two* varieties. The terminology wasn't used consistently by everyone, but most authors (and I'm using Avicenna here) distinguished lux from lumen. Lux is the brightness that one observes in fire or the sun; the luminous quality of fiery objects by which they are themselves percieved (when a transparant medium intervenes). So when you are seeing a campfire in the dark from several miles away, you are seeing its lux, not species.
However, luminous bodies produce lumen, which shines out from them and falls upon non-luminous objects and causes them to become visible (i.e. emit species). So lumen is the effect of lux on the adjacent medium and objects. It is lumen that allows species to be transmitted. Some authors viewed lumen as a non-material 'fog' that filled illuminated areas and permitted the transmission of species, and this is from whence the statement in HoH:S came; it just didn't make the elaboration that the 'light' referred to was lumen. Averroes made it clear that It is important that lumen is non-material, else species would become intermingled when they crossed. Pure forms have no matter, so don't interact.
*well, three really. There was also radiositas which is a glow emanating from non-luminous objects, but let's ignore that just now!
The most likely manifestation of Hermetic magic (in my opinion) is that CrIg creates magical lux, or magical objects that have lux like a fire. The lumen that radiates from these luminous objects is non-magical. This is by analogy with other Forms; CrAn creates a magical wolf which then radiates non-magical species. A magus with Magic Resistance is therefore still illuminated by a magical light source; and a light source created in a Ring still radiates non-magical lumen beyond the bounds of the Ring.
(Sorry for the long-winded post!)
Mark
Quite the opposite! Thanks for the post, which was very ... enlightening! 
Awesome! No need to apologize. Thanks!
Chris
Oh wow! So much signal so little noise. Thank you, that was very informative.
With a signal-to-noise ration that high, and you still apologize?!
Any time man!
Now that I've digested it...
Whereever is basked in light, there a medium called lumen. This medium carries visual species. Strong lights and weak lights will create the same medium.
Light sources also produce lux, which triggers the creation of species and controls their luminosity.
SFB faerie eyes works differently, since you can see in complete darkness.
If lux is magical and lumen is not, lux might stop at PM/Aegis but it would not stop species. Therefore those inside the Aegis would see outside normally, but would be hidden in darkness.
He said lumen, not lux, triggers the creation of species:
Let me use an example of an extremely bright flash of light used to blind everyone nearby on a dark night. This is my understanding of the what he said. The lux would be magical, and it's this brightness that would blind, so magic resistance could protect against being blinded. However, lumen would be a natural product of the bright thing and so everything nearby would become well-illuminated for the duration of the bright flash of light and everyone not blinded could see things around them well.
Chris
Correct. Good point -- I'd forgotten this aspect of light.
Correct. Furthermore, Magic Resistance wouldn't affect who is illuminated.
Medieval scholars would disagree that lumen is a medium; rather it is a quality imparted to a transparent medium (air, water) by the adjacent lux. But that's just nitpicking 
As already pointed out, it is lumen that does this, not lux. But in making this mistake you are in common with several medieval scholars who often confused the two words. This is at least partially attributable to much of this work being done by Muslim scholars, whose texts were translated from Arabic. It appears that the translators were not consistent in their use of terms.
Agreed. They cannot work through normal vision. Cats and other animals that can see in the dark emit rays of light from their eyes, enabling them to see in the absence of ambient light. The proof of this is that you can sometimes see the eyes of cats glowing at night.
(this was part of a mostly-discredited optical theory by the C13 called 'emission' or 'extramission'; however, not all parts of that theory had disappeared. This is also how the basilisk kills, and the evil eye is placed)
Lux is only a quality inherent in a light-producing object. Lux doesn't radiate, any more than my size or weight radiates (since size and weight are qualities inherent in me). You can fail to create an object with the quality of lux inside Magic Resistance (e.g. using CrIg to make a light in my hand), but that's a different matter. No one is trying to argue that.
Lumen is a quality imparted to transparant matter by an adjacent lux-producing object, that allows that matter to generate and propagate visual species. If I'm standing next to a magical light source, the air about me can now generate species, so other people can see me. Unless you feel that that magical lux should cause the inheritance of magical lumen, Magic Resistance has no effect on illumination. Personally, I feel this latter position is untenable through analogy. Magically giving something a blue coloration does not make the medium transmitting the blue species magical --- people with Magic Resistance can still see the blue colour. So magical brightness does not cause magical illumination.
(That's not to say that magical illumination is not possible. A Muto spell could grant air the quality of lumen without a source of lux. A dark room could be lit up with no light source, and those with Parma Magica within the room would not be illuminated because the air is now a magical medium and is stopped by their Magic Resistance. All individuals (including those with MR) could still see any object or being that is illuminated, because the species generated would be non-magical despite being initiated through magical means. It would be a great way for a cabal of Tyatus magi to meet!)
Mark
Best wishes,
Mark
Nice! With this second dose I think I will digest correctly now.
Those 2 posts were so helpful, I thank you from the bottom of my heart.