You can leave it in any mode you like, depending on your style of shooting.
Many people use Av as a default. Some would rather stick pins in their eyes than take it out of M. Some would never dare move away from the green box mode.
Av is a metering mode? :shrug:
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It should be 18% but I've vague memory that I read Canon had adjusted this figure but not revealed to what exactly.
The old back of the hand trick still works fine though![]()
Mainly in Evaluative, but changed when circumstances dictate.