In article ,
SteveGG wrote:

Exposure Value ( EV ) is a good measure of exposure and
is a function of shutter speed number ( s ) and apperture
number ( f ) . It is an inverse relationship, so higher EVs mean less
exposure.

Mathematically, 2 raised to the power ( EV ) = s x f x f .

Example : 1/60 second ( s = 60 ), at F/8 ( f = 8 ) ,
then EV = Log ( 60 x 8 x 8 ) / Log ( 2 ) = 11.9
( approximately ) .

For those that are math challenged:

http://www.sekonic.com/sweden/suppor...rsionchart.asp
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