Archived posting to the Leica Users Group, 2000/08/18
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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