Re: [Leica] History of coating

[Stephen Gandy <Stephen@CameraQuest.com>]

Thank you for your clarifications.

Erwin Puts wrote:

> 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.

 Sorry Erwin, I disagree.  What sources are you suggesting are better than these
?  While official publications can have an optimistic glow about them, how can
you find a better source than personal experience on how Leica products actually
perform in the field ??   the proof is in the pudding it would seem to me.
Professional papers are good sources of course, but if the result does not show
itself in the products leaving the factory, what does it matter to the real
world photog ?     For instance, I would bet there is a big discrepancy between
official Leica paper predictions of R8 reliability, and their true repair rate
(ha ha).   Scientific or engineering papers don't mean much if their predictions
don't turn out to be accurate.

>
> 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.

Would these 1946 procedures still qualify as multi coating in modern terms, with
the greatly reduced flare and increased light transmission?  Information seems
to be scarce, and comparisons to modern coatings scarcer.

>
> 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.

perhaps, but on what lenses, starting when, on which elements, and were these
older manufacturing techniques as effective as the later coatings ?  It would
seem if anyone knows these answers, it is not available to the public.

>
> 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.

in other words, Leica isn't saying . Whether Leica multicoated one lens element
of a particular lens, or no lens elements of a particular lens in 1973 is
unknown.  Even if some sort of multi layer process was used to some unknown
degree by Leica in 1973,  there is also the question of exactly whether or not
it was advanced enough to be accurately called "Multi Coating" in the same
context as today's lens coatings.

> 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.

So Erwin, you have no documentation of any kind to support your position of
Multi coating on the 40/2 Summicron. It would seem to me the fatal flaw in your
reasoning is believing that Leica would go to the extra expense of Multi Coating
its LEAST EXPENSIVE LENS at this very early date in production Multi Coating
history.     While it does make sense Leica would have started its multi coating
with their more expensive, faster lenses,  such as the 35/1.4 as discussed on
this list over the past few days,  it's completely unreasonable and unbelievable
to me that  their bottom of the line economy lens would have had Multi coating
at this early date.   If  this is your opinion, without any supporting
scientific data,  contrary to two 40/2 owners who have commented on the flare
their own lenses have,   fine.   We are all entitled to our opinions, whatever
they are.

Stephen Gandy