Why is focus point sensitivity measured in EV and not in LV?

Started Jan 7, 2013 | Discussions thread
Detail Man
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Re: Why is focus point sensitivity measured in EV and not in LV ?
In reply to bgstcola, Jan 15, 2013

bgstcola wrote:

Thanks. It's kinda confusing though. But it sounds reasonable that they mean EV at iso 100 to make a proper exposure.

It seems to be more the rule than the exception that the phrase "Exposure Value (EV)" is typically used in a manner that includes camera ISO settings (even though actual Exposure is not related to ISO settings). The identity that is (seemingly) almost always being referred to is:

"EV" = LOG base 2 ( ( 100 / ISO ) x ( (F)^(2) ) x (S) )

where:

ISO is ISO setting;

F is F-Number;

S is Shutter Speed.

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