----- Original Message ----- From: "Ellestads" <ellestads@xxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx> Sent: Wednesday, July 08, 2009 7:52 AM Subject: [rollei_list] Re: Lens coatings and veiling flare.
Please be careful cleaning interior surfaces of older coated lenses. Many of theses lenses (including Leica) ued soft coatings on the inner elements.Cleaning can reduce those coatings. Tim
Kodak certainly used soft coatings on some early coated lenses. These were premium lenses made beginning in about the late 1930s. I don't know what process was used to coat them but the coatings are _only_ on protected inner surfaces and are very delicate. While Marc beleives that Smakula, of Zeiss, invented hard coating I am not so sure. Zeiss may have had this technology but the record seems to show it was developed by a reseach group in the US during WW-2. Vacuum coatings can be relatively soft and the early ones were. What was developed here was the technique of baking the coatings in vacuo. Previously the coated lenses were removed from the vacuum chamber and baked in a separate operation. Baking in the coating chamber results in coatings nearly as hard as the glass. This method was developed as part of a research project for military optics. I don't know what instruments or devices it was applied to. The familiar Bausch & Lomb Navy binoculars appear to have been coated after manufacture. There is a good history of hard coating available at the Society of Vacuum Coaters web site:
-- Richard Knoppow Los Angeles, CA, USAdickburk@xxxxxxxxxxxxx
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