QUOTE (TBRMInsanity @ Jan 22 2010, 12:01 PM)

Is LOS defined in the book as "you must see the target" or is it "you must be able to see the target"? If it is the former then yes blinking or turning your head away will break LOS, if not, then simply having the ability to draw a direct line of sight from the target area to the mage would mean you have LOS. I tend to think (and run my game) that LOS is the ability to see the target and not you must see the target currently.
The idea of LoS is based on drawing a line to determine if it is
possible to see a person or not. The theory behind it though is that when making use of that LoS you actually
do see that person at the time. It is after all possible to draw LoS to a person through a pitch black room, but that doesn't mean that you can actually make use of that LoS because you can't actually see the target.
So yes, LoS is the theoretical ability to potentially see a target, but it is generally assumed that LoS requires you to actually see the target. This basically represents the fact that you have a nearly 360 degree field of vision when you include turning your head and such so you don't have to worry about which way you're facing.