T3D Swapping lens groups on old cameras

[erker@xxxxxxxxxxxxxx (Greg Erker)]

Hi all,

  I am presently building a medium format
stereo camera using two Ricohmatic 225 TLRs.
See my web page for photos:
http://www.angelfire.com/ca/erker/twin225.html

  The cameras have 80mm f3.5 Rikenon tessar
style lenses. I presently have 5 sets of Rikenon
lenses (from 225's and Diacords) in a variety
of conditions.

  I am planning on testing the lenses to find
the best matching pair (for focal length).
Hopefully I can do this to 1% or better.
(see my web page for the method I plan to use).

  If that isn't possible with my 5 lenses I
had though I might mix and match the front
and rear lens groups to try to get a better
match.

  But Eric G. dug up this warning about doing
that:

>According to Master Camera Tech Ken Ruth, this is not a good idea.
>
>He contends that before the 70s, fine optical glasses had to be cooked
>up in relatively small batches (little automation) and there was fairly
>significant variation from batch to batch. Just as the tolerances for
>grinding were far greater than today, the tolerances for refractive
>indices were also far greater, and batch-to-batch matching of lens
>elements was part of the lens-making equation.

  Does anyone have any additional or contradictory
information on this subject. I'd appreciate it.

Thanks - Greg



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