[rollei_list] Re: Tessars
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Sat, 2 Jun 2007 22:15:27 -0700
----- 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, USA
dickburk@xxxxxxxxxxxxx
---
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