As Raze states, it is the use of source magic that will get you into trouble. For example, you can summon the standard incarnate around magisters and they will gawk at it saying things like, "and here I thought I'ld seen everything." That is because summoning the standard incarnate isn't source magic.
On the other hand, if Ifan were to summon his soul wolf in the Blackbull Tavern, that is source magic and would aggro any magister in range. Ok, the location doesn't matter, I just couldn't resist an in-game lore reference.
Spirit Vision is a type of source magic, it just doesn't require the use of a point of source. That is why magisters get upset when you use it near them. I chose my questions for Raze thoughtfully from in-game experience of testing the limits of what I could get away with.
Perhaps another example would help as well. If you summon the Scoundrel Wind-Up Toy, summoning it will not provoke anyone because it isn't source magic. However, when it blows up, it may damage people or items people own. This may upset them enough to attack.