Archived posting to the Leica Users Group, 2000/03/06
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Alas the only thing worse than my memory is my math but I do believe you are right Marc. Mr. Rakitzis emailed me privately with the following information which I hope you all will take care and not let it fall into the wrong hands. John, here's the sequence of powers of the sixth root of two, which gives you the third-stop increments you want: 1.000000 1.122462 1.259921 1.414214 1.587401 1.781797 2.000000 2.244924 2.519842 2.828427 3.174802 3.563595 4.000000 > From: Marc James Small <msmall@roanoke.infi.net > > At 10:17 AM 3/6/2000 -0700, John Collier wrote: >> This from a long time ago, with my memory that is about a week, but I >> thought it went: > > The surface of a circle is pi x radius squared. I don't have lenses at > hand, but roughly, the putative radius of a 50mm f/1.4 lens is 17.86mm, > that of an f/1.5 lens is 16.66mm. Squaring these, the ratio is 318.9:277.56. > > Reducing this gives 1.14, or 1 1/7. >