----- Original Message ----- From: "Marc James Small" <marcsmall@xxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx> Sent: Saturday, June 02, 2007 8:53 PM Subject: [rollei_list] Re: Tessars At 06:33 PM 6/2/2007, Richard Knoppow wrote:Kodak used Ektar as a trade name for its premium quality lenses. Ektars are of many designs. Zeiss made Tessars of several speeds. Those used for large format work were mostly f/4.5 or f/6.3. The f/6.3 version has a slightly larger field, and is smaller and lighter. Kodak's LF lenses were made as Ektars mainly as f/4.5 lenses but there was also the Commercial Ektar series of f/6.3 lenses. These are exceptional and nearly apochromatic. A version with soft coating on internal surfaces was sold as the Eastman Ektar. Kodak made a very large variety of lenses, mostly for its own cameras, but some as individual items. All of the Ektar series are corrected for lateral color. Its difficult to know what Zeiss, or rather the Zeiss's were up to following WW-2. Certainly they would have been experimenting with the new glass types becoming available and may have applied these to Tessar type lenses. Because of the properties of these glasses its possible to use them to reduce all aberrations. AFAIK, Kodak did NOT use lanthanum glass in any of the medium or large format Tessar type Ektar lenses, it may not have proved economical to do so. The new Google patent search is quite valuable for finding older patents. The USPTO site allows only number searches for patents issued before 1976 where the Google search allows all sorts of text criteria such as inventor's names and assignees. So, one can look up Zeiss, or Ludwig Bertele, and find their patents.
--- Richard Knoppow Los Angeles, CA, USAdickburk@xxxxxxxxxxxxx
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