optical design.

[captyng@vtx.ch (Gerard Captijn)]

Although lens design is only one of the many elements that determine the
final picture, there may be Leica photographers interested in the subject: I
am one of them. Those interested may want to have a look at two optical
programs on the net, Zemax Demo, an optical design program, and Zemax
Lensview, a file of lens patents, both of which you can download and play
with. Both have limited functionality but there is enough left to be of
interest.

URL is http://focus-software.com/demo_z.html

Zemax Demo, the raytracer, includes the constructions of the Summicron 50mm
f/2.0  (dbgauss.zmx), the Elmar 50mm f/2.8 (tessr100.zmx) and the Elmar 90mm
f/4.0 (cooke.zmx). The program traces rays in any wavelength you like,
ray/opd fans, spot diagrams, transfer function (MTF), etc., and has the
catalogues of Schott, Hoya, Ohara and other glass manufacturers build in. It
can handle non-spheric surfaces and optimizes in split seconds any variable
in any optical system.

Zemax Lensview offers an interesting collection of optical patents,
including constructions from G.H.Cook (Taylor, Taylor & Hobson), Pierre
Ang=E9nieux (Ang=E9nieux) and L.J.Bertele (Zeiss/Wild). There is also a=
 patent
from "champion extraordinaire" Ernst Wandersleb (Zeiss) who wrote an entire
book about the impossibility to construct good large aperture extreme
wideangle lenses because of light fall-off (Cos4 law). Shortly afterwards
Zeiss and Schneider build the Biogon and the Super Angulon, proving the
contrary.

I have at home a little book "Nieuwe optische constructiemethoden", written
in 1945 by General-Majoor L.E.W. van Albada (yes, the Dutch optical engineer
who invented the Albada finder). The book explains how to calculate, grind
and build your own lenses. One of the examples given covers the design of
your own homemade triplet. Approximately one week work for developing a
badly corrected first version, using the special ray drawing method that van
Albada developed. Zemax will do the same work in less than a second and
demonstrates todays' designers' ability to optimize a design with a computer
to a far higher degree than in van Albada's days.

If you want to get some (rather basic) understanding of the problems of
Lothar K=F6lsch at Leica or Dr. Hohberg at Zeiss in calculating new glass,
download Zemax and start playing. Maybe nice for a rainy day when the light
outside isn't too great and the darkroom unavailable.
Gerard Captijn,
Geneva, Switzerland.
Email: captyng@vtx.ch
Fax: +41 (22) 700 39 28