Re: Summicron formulas

[Ichiro Suzuki <suzuki@blatz.cs.uwm.edu>]

>From: Jeffrey Frey <jeff@eng.umd.edu>
>Date: Sun, 5 Feb 1995 17:32:01 -0500
>To: leica-users@mejac.palo-alto.ca.us
>Subject: Summicron formulas
>
>A guy I've been corresponding with on rec.photo.advanced has said that "some
>Japanese" believe that the formula for the original 50/2 rigid Summicron was
>different than that for the 50/2 collapsible Summicron (made at the same time) and is, in fact, much superior.  Does anyone know if part or all of this 
>statement is true?
>
>Jeff

I read in three books published in Japan that the rigid Summicron 50/2 
used a formula different from that for the collapsible Summicron 50/2.
Both are of 6-group-7-element design, but the drawings of the two 
versions clearly look different.

My own question is whether there was *only one* formula for the rigid
Summicron 50/2, or more than one.  The author of one of the books I
mentioned states ``It seems the formula of the Summicron 50/2 was 
changed several times without any announcement from Leitz." 
(He is talking about what we know as ``the(?!)'' first generation 
6-group-7-element Summicron 50/2 lenses, not the later ones.)
I don't know if ``several times'' is really true. Can anyone help?

Another question: There was a period when Leitz produced both the
rigid Summicron 50/2 and the collapsible Summicron 50/2.  I am tempted
to believe that each had its own formula at that time, which means
that the two formulas overlapped in time.  Any idea?

Yet another question: Do the rigid Summicrion 50/2 lenses have
*identical* formula as the near-range Summicrion 50/2 lenses
from the same period? That is, is the focusing mechanism the *only*
difference between the near-range lenses and the rigid ones?

I don't know if the newer design is ``much superior.''
I tend to think that each has its own character.
Has anyone tried both?

Thanks for reading. --Ichiro

PS: I am a Japanese, but that is just a coincidence. :-)