The only way to compare different camera battery life is for everyone to follow a standard.

That standard has a set pattern of what is done and for how long.

It can not answer all of the possibilities and variants that anyone can imagine.
So there is no answer to the questions you asked.

If you really want to get into the nitty gritty of the formula used you can look here:

http://www.cipa.jp/english/hyoujunka/kikaku/pdf/DC-002_e.pdf

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