Best review of the basic science I have seen online: http://johnlind.tripod.com/science/ http://johnlind.tripod.com/science/ The the lens calculations are a wh

Best review of the basic science I have seen online: http://johnlind.tripod.com/science/ http://johnlind.tripod.com/science/ The the lens calculations are a whole 'nother ball of wax, but here's the quick skinny on the exposure value system: Av + Tv = Ev = Sv + Bv Exposure value: Ev Aperture value: Av = log2 (f^2) Time value: Tv = log2 (1/t) Speed value: Sv = log2 (0.32 * ISO) Brightness value: Bv = subject luminance in foot-Lamberts