Would a mage providing spell defense to himself notice if someone came within his LOS with an invisibility spell/mask spell/camoflage spell/etc.?

I believe the mage would get the advantage of his spell defense to resist the illusion and the pool being used up would be something the mage would notice.

In this case, the mage might not know which spell he was potentially affected by, but he knows there was some spell and might check astral and see the invisible offender. (At least our PC's would)

Sound right?

Exactly right as far as I'm concerned.

I'd say no. Spell defense only applies if the defended subject is the target of a spell. In the case of an Invisibilty spell, the target is not the person resisting the illusion, but rather the person being hidden by the illusion. As such, the defended subject wouldn't be eligible for spell defense dice. They would still get a spell resistance check vs. Intelligence, however.

[edit]
Now if the defended subject were being targeted by an Invisibility spell involuntarily, that's a different story...

What Spooky said.

Emphasis mine on the following...

Magic in the Shadows, page 55:

"Indirect Illusions [such as Invisibility] are cast on a subject person or area. Anyone who views that person or area is a target of the spell."

Shadowrun 3rd Edition, page 183:

"Whenever a [character that is the subject of Spell Defense] is the target of a spell, the magician senses it and may allocate Spell Defense dice to 'block' the incoming spell."

What Spooky said. And a Leopard Shaman gets even less due to his totem penalty to resist Illusion spells.

I know it's not exactly cannon, but with the ruleset we use, unless a character has a reason to resist an illusion (i.e., he/she is suspicious, illusion or invisiblity does something that's out of place) they don't resist.

In the case of the mage with spell defense dice allocated .... tough call. I think, in the low magic incidence cases we use in most of my games, the mage would be allowed to use the dice for seeing throught he illusion if he/she had any reason to do so ... basically, it would be easier for him/her to see through the illusion. They could also use them randomly every 3 seconds or so, just as a precaution. If a player was that on guard, I'd let them roll them a few times, seeing nothing, then say they saw through whatever illusion when the time came right.

Yeah, I'm w/ Spooky here. Mages never know they resisted an indirect illusion spell. Then again, Mages (or anyone) never know they resisted a Detection spell either in my games.

Sphynx

Indirect Illusions are still magic and have an effect on anyone they come in contact with. While a mage might not know that someone has Invisibilty cast on themselves, they will know that some kind of magic is affecting him and those he's protecting, and he can take steps to help resist it. He can then alert his fellows that something is amiss and take more steps to figure out what it is. This applies equally well to area-effect detection spells and other similar magicks.

But only as long as he had Spell Defense allocated to begin with; if not, he's as oblivious as anyone else.

The rules support this as previously pointed out, too.

Doc I whole heartedly agree...
Invisiblity doesn't change you as the caster, it doesn't bend light or anything taky like that. It affects everyone else as a SEP from Hitchhiker's Guide to the galaxy. They don't see you because they don't want to...the spell as I see it is psuedo mind affecting, but not invasively. So you don't see them, don't know they are there unless you have an active protectant against the magic, which Spell Defense would take care of, allocate the dice, you notice the invisibility affecting you(as it does) and take actions.

Hardly. With Invisibility, they are literally invisible to those who don't have Spell Defense/Ultrasound. With Disregard, you just don't care that the person is there until they do something life-threatening to you.

Edit: You get a chance to defeat the spell every time something is done to you that is threatening (life, social, etc). It's in Awakenings from SR2 if anybody cares to take a peek at it.

It was more sardonic than serious. Sorry.

Eh, I just wanted to keep the SR newbies from going "Ohmigosh! Disregard sounds soooo cool!" then promptly remake it and kill their GM's plans every run.

Yes. My team did that once. Never again will I allow such nonsense to take place. House rules rock.

Argh! The first rule of Shadowrun (Never trust a single sourcebook) strikes again!
Thanks for the clarification, Doc.

I ran the rule quotes by our SR group and one of the mages plans on sustaining a Force 1 Illusion spell before ambushing anyone. As he jumps around the corner, the opposing mage would sense that he (and anyone he is protecting with spell defense that can see the PC mage) is being targeted by some spell and will likely provide use spell defense dice to protect himself and others from the unknown spell.

Then, while the mage's pool is decreased, the PC mage plans on launching the real spells.

As I read what Doc Funk wrote, that works ... right?

Prior to the good doctor's findings, I would have called you daft. However, in light of this new evidence, that seems to be a valid tactic. If the target being protected doesn't know the nature or force of the spell (and they won't, unless they've had time to assense the spell first), then there's a good chance that the protecting mage will burn spell defense dice 'just in case'. Combine this with a relatively cheap (drain-wise) spell, - Entertainment, for instance - and you'll have an edge going into combat. Works even better with a more functional class of spells, like Detection.

And before anyone mentions it, yes, Entertainment is automatically resisted by non-voluntary viewers. It doesn't mean they aren't considered valid targets for casting, however. Just think how pissed off the defending mage will be if/when they find out they burnt dice against a spell that wouldn't have affected them anyway!

Yeesh... lots of room for abuse here....