Derivation of Exposure Valuesgreenspun.com : LUSENET : Large format photography : One Thread
Can anyone tell me how the numerical Exposure Values (EV) are calculated? Is there a standard mathematical definition that relates a given speed and aperture to an EV number, or are EV's just an arbitrary sequence with each integer representing one stop?
-- Nick Thornton (Nick.Thornton@liffe.com), October 19, 1999
As per Norman Goldberg's "Camera Technology - The Dark Side of the Lens":
2^(EV) = N^2/T and EV = 3.222 log (N^2/T)
where: EV = exposure value N = f-stop T = shutter speed, seconds
-- Bill C (firstname.lastname@example.org), October 19, 1999.
Yes, each interger does represent one stop...
-- Bill Glickman (Bglick@pclv.com), November 01, 1999.