I'm pretty sure the answer is going to be no protection, but i'd just like to know

Without wearing armor, investing in the mage armor perks gives you x2 the protection of the specific spell used. But i see NPC's in game casting it while wearing armor, so does it give x1 protection while wearing physical armor or (as is suspect) just none at all ?

Edit: Is there any positive use at all, to casting it while wearing armor & fighting ?

Thank you.

Every -flesh spell has a base Armor Rating it gives. For example, one of the spells increases your Armor Rating by 40. With one rank in Mage Armor, you get 2x effectiveness, so that 40 AR spell will now give 80 AR. However, this only works while you're not wearing armor. If you are wearing armor, you only get the base effectiveness (40 AR), but if you take off the armor, you get the increased effectiveness (80 AR). The point to using the spell while wearing armor is to make you more durable than you would be without the spell, as you still get the base effectiveness added on top of the armor's physical AR.

So you CAN get the base protection (x1) of the spell to work even with armor. Learned something.

Thank you.