Archived posting to the Leica Users Group, 1996/05/29
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 03:11 PM 5/29/96 +1200, Michael Moffatt wrote: >I was lead to believe (today in fact) by an excellent repairer, that the >inside elements of leitz lens' (in this case an old M-series Summarit) had >a liquidish type coating that is smudged or removed ON CONTACT... Close, but not quite the whole story. Alexander Smakula perfected lens coatings in 1935 whilst at Zeiss; this involved the application of fluoride deposits by means of vacuum coatings. Zeiss immediately obtained a patent on this, which was "close-held" for military reasons until 1940. The patent then had a 20-year life. So, until 1960, no other German manufacturer could use vacuum coating technologies. Leitz, and others, used 'drip coating' techniques which left a moist coating. This coating is quite soft and, often, dries in a pattern similar to that of a lake-bed -- minute cracks quite visible under magnification. Many dealers don't know about this and will describe a lens as having 'wipe marks' when, in fact, all it needs is a couple of weeks in John Van Stelten's hands to have the front element recoated. The coating of internal elements only was a frequent result; even Zeiss did this on some late Prewar lenses. A coating on an internal element does not dry so readily. The use of vacuum coatings was independently developed in the US -- by Wollensak, I believe -- and in the UK a few years after Smakula's work, so the Zeiss patents did not apply in these countries. Marc msmall@roanoke.infi.net FAX: +540/343-7315 Cha robh bas fir gun ghras fir!