Ease Factors for Aiming Spells

When a magus aims a spell at someone how do you determine the Ease Factor? Does the target get a Defense roll, and if so do shield and weapon bonuses apply? What if the target is an inanimate object? I'm assuming distance plays a part in all this.

The aiming total = Perception + Finesse + Die (stress die if stressful situation, like combat, or simple die otherwise). This generates an attack total.

The target of the spell gets a Defense roll to determine whether the spell "hits" or not. Whether they get a shield and/or weapon defense bonus is situational: you can't use a shield or weapon as a defense against a pit opening up underneath you. Pretty much here you get your dodge as your defense. If it is a rock being dropped on your head, depending upon the size of the rock a shield may come into play, but the weapon would not. If someone conjures a sword and moves it at you to impale you, I would give both shield and weapon as a defense.

There is no general rule. It depends on what you are trying to avoid.

Yes, use your common sense if a weapon or shield can be used against the effect of the spell or not. I think in must cases Dodge should be used.
I see no range modifier in the rules.
In the case of an inanimate object I would use the general ease table. I think aiming a human sized target is 'easy' but it's just me.

Thanks, much appreciated!

Got people coming over at noon for our first Ars game ever.
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Wish me luck.