Archived posting to the Leica Users Group, 1997/04/24[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
> > You're better off with the Elmar M, a nicer and better performing lens > > which gives you an additional "half" stop (Ed Meyers says 1/3, I say 2/3, > > the heck with it) over the Hektor. > > It's .27 of a stop if anyone really cares 4.5 squared is 20.25, 4 squared > is 16, and the ratio is 20.25/16 = 1.27 > I changed my mind about this. Although an f4 lens produces an image 127% as bright as an f4.5 lens, Ed is right it is 1/3 stop brighter. If you take the LOG of the common f stops 1,1.4,2,2.8,4,5.6 you get 0,1.5,3.0,4.5,6.0,7.5. The LOG of 4.5 is .65 so f4.5 is 1/3 stop faster than f4, 2/3 stop slower than f5.6.