Archived posting to the Leica Users Group, 2000/08/18

[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]

Subject: Re: Vs: Vs: [Leica] M-multicoating, was: Rokkor story
From: "Henning J. Wulff" <henningw@archiphoto.com>
Date: Fri, 18 Aug 2000 21:01:23 -0700

At 11:00 PM +0200 8/18/00, Raimo Korhonen wrote:
>I do not doubt it - but my Summilux 35 from 1976 does not have
>multicoating - so what was multicoated in 1957?
>The Pentax multicoating has 7 layers and Fuji EBC has 11 layers so there
>is a difference. And I "believe" that Optical Coating Laboratory Inc. was
>needed to make multicoating commercially viable and they had some
>important patents.
>All the best!
>Raimo

Have you had it tested? If you do, I think you would discover that some
coatings are multi-layer. All 35 Summiluxes have had this.

At what point do you consider multi-layer coating to be "multi-coating"?
Pentax seemed to feel that for PR purposes, their 7 layers qualified. As
Erwin has stated quite correctly, multi-coating is something that has to be
done in conjunction with the lens design, and is not something that
necessarily provides the same benefits with all glasses and designs.
Whether a lens has 7, 11, 3 or whatever layers should be determined by the
overall design, not PR pressures.

When Nikon started using multi-layer coatings around 1970, they tried to
stress that some lens surfaces benefited from multi-layer coatings, some
did not, and named their system Nikon Integrated Coatings (NIC) to point
this fact out. That design concept has not changed with most of the
manufacturers, including Zeiss and Leica.

Optical Coating Laboratory, which I believe was a division of Raytheon, did
have some patents on some coating technologies which Pentax and various
other manufacturers used, but you have to understand that coating
technology, and the transition to multi-layer coatings was not a one-time
step, but a developmental process. As such changes in techniques and new
insights lead to continual improvements on a regular basis, even now, and
saying that Optical Coating Laboratory has some patents means something,
but certainly not everything. There was definitely research and material
advances in this area in the 50's already. The principles of multi-coating
were known a long time ago.

I did some work in optics in the 60's, and also worked for a while at
Siemens in a physics lab where, among other things, I studied vacuum
deposition production techniques. Multi-layer coatings were part of this,
and it was no secret.

Leitz's 1950's multi-layer coating techniques may not have been as
sophisticated as the systems that Pentax and Optical Coating Laboratory had
later, but that does not mean they did not exist.



   *            Henning J. Wulff
  /|\      Wulff Photography & Design
 /###\   mailto:henningw@archiphoto.com
 |[ ]|     http://www.archiphoto.com