You can notice spells when they are cast and in some other specified circumstances.
You disagree with my assertion that due to the description on pg 280
All magic is perceptible and subject to those Perceiving Magic rules. Fair enough, but if you can't provide a citation that supports your claim that spells are only noticeable under certain circumstances you'll understand why I consider your claim the weaker one.
Noticing spirits are present in the Astral is called out as being fluffy and mostly tied to the spirits being lazy and actually touching the mundanes aura, not if its sitting quietly in a corner no one is near.
And yet that's counter to what pg 280 says. It says nothing about the spirit needing to touch the observer's aura in order to grant the observer the chance to notice the spirit's presence. And at the same time, it does give the implication that the spirit need simply be in proximity as we have a definitive statement in "spirits sometimes cause the air to shimmer, even from astral space". At best the only room for disagreement about this statement is a philosophical argument about whether there's a shimmer there to be seen if noone is there to see it. (the tree falling in the forest with noone to hear rehash) However if you're going to argue that a character can only see shimmers if the spirit touched that character's aura, I'm going to dismiss your argument as based on "this is how I think SR should work" rather than what SR itself is telling us about how it works. Gimme a citation to support your opinion or all you got is opinion.
Also as Marcus pointed out if sustained spells are just obvious its self defeating. It also makes a bunch of meta magics worthless as he pointed out. The whole let me invest 2 metamagics worth of initiation(masking & extended masking) into it so that even mages cant tell I have physical mask up is unless they manage to break my masking meta magic or resist my physical mask spell is self defeating when they go i beat a thresh hold 1 perception test to see the magical sparkles around you because you cast a bad ass force 8 physical mask spell. It means mages are by default the Pinkest of Pink Mohawk characters unless and untill they get to a spell casting skill of 10+ so that even medium force spells require at least 3 or 4 hits to notice.
Going backwards to front on this: So what if mages
are inherently very pink mohawk? There's a pretty big suspension of disbelief if you're running a "black trenchcoat game but with magic" anyway.
But more to the point, keep in mind that the "but invisibility is worthless!" counter is a
straw man fallacy: the example on pg 280 never says anything about the magic's effects being countered by tells, nor that the event of successfully perceiving that magic is present gives information to mundane senses about what the magic is doing, or even where it exactly is located. So no, there's no reason to presume that just because a powerful invisibility spell might be perceived under the Perceiving Magic rules there's no reasonable justification in saying invisibility magic is worthless because it A) still doesn't let the observer know where the invisible person is and B) provide the observer the knowledge that the magic noticed even was specifically an invisibility spell.
They have some specific rules like if your the target of a mental manipulation spell that get around this, also some of the spell descriptions themselves imply noticable effects that I would use to apply the notice a spell rules even when its being sustained. The armor spell is one of the top of my head as the spell description clearly states you have a nice magical force field glow around you while the spell is active.
Clearly a case of due cause to invoke the third paragraph of the Perceiving Magic rules (pg 281).
I also personally apply this to the ghostly Mostly invisible hands you get from the magic fingers spell to sight some specific examples.
More power to you.
How ever there are some spells Like body glove, which is the Armor spell with a slightly higher drain code the specifies its the stealth ops version of the armor spell that functions like the armor spell in all ways just with out the distinctive glowing forcefield effect so you can have it active without the glow in the dark problem that prevents you from sneaking around.
Citation would be appreciated, but going off what you're saying if it's just an Armor spell without the language that it has a visible glowing field, then we're back to the first two paragraphs of the Perceiving Magic rules. Just as a guard noticing "something magic is afoot" when an invisible target is lurking nearby doesn't invalidate invisibility magic, a guard "noticing something magic is afoot" doesn't invalidate sneaking armor in to someplace you're presumably not supposed/encouraged to have it.
Also as pointed out pretty much the entire illusion school of magic gets invalidated by this approach....
Aaaaaaaaand... no it doesn't. Not because I say so btw, because you failed to provide citations that support your claim. And some of your claims (like you only get a chance to perceive a Deflection spell if you happen to shoot a bullet and might notice the deflection) are demonstrably false.
In the end you are choosing to read and interpret the rules a little different then most people I know who play the game. And that is ok and its always a learning process when you sit down at a new table to feel out the GM and see how he handles things. That being said they way you are interpreting things is so self defeating I cant accept that that is how it should work.
I don't see where there's something to object to in the assertation that "according to the SR rules governing Perceiving Magic, on pages 280-281 of the 5th Ed Core Rulebook,
any magic is potentially perceptible". May not be popular, may not jive with prior editions (and I'm not prepared to agree it's novel to 5th, just no point in arguing about prior editions) and hell maybe it is game changing. Nothing wrong with any of this.
Its like saying every point of armor you have give results in +1 DV when ever your shot.
No, no it isn't. Me pointing out the rules as they are written isn't like you making up entirely new rules.
Your making the only viable play style for a mage to be the pink mohawk combat mage that just floats down the middle of the street and is visible form low orbit by your naked eye because he is lit up brighter then most million candle spot lights because of his sustained spells.
I'm not making anyone walk around with say, Force 10 or 12 sustained (or quickened!) Attribute Modification spells. If you're doing stuff like that, then you're already playing Pink Mohawk.
Honestly, if you're going to use magic in a Black Trenchcoat game, you need a rule like the Perceiving Magic, or else there's no incentive to ever use magical analogues to holdout pistols rather than assault cannons.
...I cant influence the guards to do anything because as soon as he walks back in the guard shack and says everything is fine the other guards go Ohh your covered in magic sparkles hit the panic button and call in magic back up etc.
If we're going to be hyperbolic about what each other is claiming by implication, then allow me to shed a tear for Mages being inferior to dedicated Faces and Covert Ops Specialists at Faces' and Covert Ops Specialists' own jobs.
But to treat your comment with the seriousness that I'm sure you'd want: lets say you do influence the guard to do something, and while he fails to resist he does succeed on noticing the spell. Doesn't mean he's going to go press the panic button instead of what you influenced him to do via the spell. Come on now.
Edit: In fairness, didn't notice your complaint was about the
other guards hitting the panic button. Yeah, that's kind of the intended point about the Perceiving Magic rules, imo. You need a better plan than "have the Mage cast a spell at the problem". You'll have to incorporate your magic
into a plan rather than being the plan all by itself. I see absolutely no problem with this.