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Roger Hicks
08-24-2009, 05:15
Anyone interested in lens coating could do worse than to go to http://www.svc.org/H/H_References.html where they will find a link to a paper (in PDF format) recording the transactions of a conference in October 1943. From this paper it is clear that interest in coating began at around the time of the First World War and that by 1943 'superhard' baked coatings were already well known. There is also information on what will and won't remove these coatings, which were pretty much what was adopted when lenses started to be coated generally in the 1950s using baked-in-a-vacuum MgF coatings. Multi-layer coating is discussed with the proviso that no-one will need to worry about it 'for a year or more'.

Other desultory research indicates that experimental multicoating was tried by both Leica and Zeiss during WW2 and that British patent literature indicates that the 35/1.4 Summilux was multicoated, at least on some surfaces, from its introduction in 1957, though I have not verified these sources. If anyone knows of other dated papers, patents, etc., on coating technology -- not internet speculation -- perhaps they would be kind enough to post links or give references.

Tashi delek,

R.

outfitter
08-24-2009, 08:42
Many thanks for a fascinating document. The history of the process of hard coating, which goes back to at least WWI, puts in perspective the oft repeated claim that Zeiss "invented" the process in the 1930s and that it was top secret during WWII. I had always wondered why my WWII binoculars seemed to have more durable coatings than WWII Zeiss lenses.

furcafe
08-24-2009, 10:09
Here's what Marc James Small recently wrote on the Zeiss Ikon Collectors Group list:

Zeiss owned the German patent rights to the
vacuum-coating method, and only they and their
licensees (JSK and Voigtländer from 1947 or 1948,
and Steinheil and Kilfitt later) could use
it. Leitz was forced to use the drip-coating
method which produced a soft coating which
rapidly dried out. (Buyers' hint: the residue
will LOOK like cleaning marks, and dealers often
sell these lenses at a discount -- take a loupe
and examine the surface and you will see what
looks like a dried lakebed. A quick trip to
Focal Point and your lens will be better than new.)

The Zeiss patent expired in FEB 1960, and Leitz
then shifted to the hard-coating method immediately.

Kodak AG used hard coatings from 1948 but their
right to do so derived from the 1943 US Alien
Properties Act, which gave Big Yellow open access
to the Smakula method -- and, in any event, Kodak
(and Wollensak and Ross in the UK) had
independently developed the vacuum-coating
technology around 1935. Kodak probably started
selling coated photographic lenses before Zeiss
did, though this is an issue of contention over at the Society of Lens Coaters.