Chris Brogden said: > On Wed, 5 Mar 2003, Gregory L. Hansen wrote: > > > > So... is 1.2 half a stop faster than 1.4, or slightly less than half a > > > stop? I realize that this make no practical difference, but I'm curious > > > nonetheless. > > > > Real half stop step would be f/1.14. The difference in exposure increase > > versus f/1.2 is 7%.
Sorry, did my exposures wrong. Light in is proportional to aperture area, which is proportional to 1/f^2. So (1/1.14^2 - 1/1.2^2)/(1/1.4^2) = 15% difference between 1.4 to 1.2 and 1.4 to 1.14. > > Ok. Am I correct in assuming that the lens, even though it's labeled as > "1.2", actually opens to 1.14, or whatever the correct value is? If this > is the case, then the difference between the 1.4 click-stop and the 1.2 > click-stop is half a stop, right? On what the 1.2 on the lens "really" means, I have no idea.
