[Leica] History of coating

["Erwin Puts" <imxputs@knoware.nl>]

The information on which most of Lug discussions is based, is extracted from
product brochures, company leaflets, articles in the popular photographic
press, personal experiences and the many books about Leica and photography,
which in a large part are based on product brochures etc.Generally this
information is not the best source for the advancement of knowledge.
In a report from the Naval Research Laboratory from October 3, 1946, a
number of scientists report on the state of the coating technique in the
Zeiss and Leitz factories in wartime. They note specifically that both
companies use multiple layer coating as a technique, but because of its
costly procedure, only experimentally. It can thus be established that the
technique multilayer coating did exist at Zeiss and Leitz.
In a report of the BJP from Otober 24, 1975, also referenced in The Leica
Collectors Checklist, it is stated that Leitz used multiple layer coating in
the Summilux 1.4/35 (British Patent Literature from 1957). Reports in the
Journal of Optical Society of America in 1957 discuss the use of multilayer
coating based on progress in the leading optical firms.  ML-coating has been
used since the fifties in many optical instruments, but mass production was
not yet possible. The innovation of OCLI and Pentax is NOT to invent the
ML-coating, but respectively to design a technique for muli layer depositing
in an economical way and to make a marketing hype out of its application on
Takumar lenses. Other firms already used it, but did not advertise it.
The Summicron-C 2/40 coating. In Gunter Osterloh's handbook on Leica M it is
stated that Leitz policy dictates that no information is given about the
type of coating of lenses. Leitz position is simply that coating is part of
the optical design and single and multiple layer coatings are applied as
deemed necessary and no specific references are to be made. And even today
Leica is not promoting the fact of ML-coating although all their lenses now
employ MLC.
So given this directive it is logical that Kisselbach (Leica employee)
simply notes that the S-C is coated. And in the same vein magazines like PP
and MP will report what they know: the lens is coated. They are right in not
speculating about the use or absence of MLC as you cannot know  without
given specific facts from the company and as the company says they will not
disclose the info, that is as far as they can go.
Given Osterloh's position his statement reflects the status-quo about the
S-C: without direct access to the company info (which is not disclosed or at
least may not be publicized) we cannot infer from the designation that the
S-C is coated , that is it therefore not multi-coated. This would be a fatal
flaw in any logical reasoning.
Erwin