Ok, I've been reading and re-reading and experimenting with exposure.

I have 2 questions. The first question is purely academic, I do NOT have delusions of grandeur, but it will add to my fundamental knowledge on how stuff works. Ok, here goes:

Q1: When I, or ENG cameramen, decide to "blow-out" a background, to achieve decent exposure in the foreground, how does this blown background "cover" being legal for broadcast?

Q2: The XM2 has a range of zebra "sensitivity" in terms of percentages. Are these "percentages", percentages of 100 IRE which equates to pure white?

I have read the following too:

Zebra Stripes- How much is too much?
http://www.dvinfo.net/conf/showthread.php?s=&threadid=13523

Using Viewfinder Zebra Display
http://www.greatdv.com/cameras/Zebra.htm

Once I get answers to these questions I, undoubtedly, may have others.

Grazie