Hello: There's a term for making things more complicated than they are, and I don't remember what it is, so I'll get to the point (irony?).
exposure time multiplier = [(higher f-stop number)/(lower f-stop number)]^2 Don't need the logarithmic factors - I think I had them on both sides of my equation before so they weren't necessary. example f 5.6 and f 1.4 are 4 stops apart, so exposure time is doubled 4 times when going from 1.4 to 5.6, or multiplied by 2^(#stops). Also, (5.6/1.4)^2 gives same result, and works fine for large f-stops (512/16)^2 = 1024 = 2^10, or double 10 x. Ignoring other problems with exposure, no need to round off your odd f-stop number corresponding to the size and distance of your pinhole. I used f 16 because it gives me relatively long exposure result from light meter to multiply. Murray
