[rollei_list] Re: [rolleiusers] 4x5
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Sat, 3 Jan 2015 23:30:57 -0800
----- Original Message -----
From: "Eric Goldstein" <egoldste@xxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Saturday, January 03, 2015 7:59 PM
Subject: [rollei_list] Re: [rolleiusers] 4x5
Glass types improved dramatically in the post war period
and higher index
glass become more affordable for manufacturers... Many
formulations were
recalculated and improved...
Eric Goldstein
This was partially because of the break up of the
monopoly the Germans had on optical glass before WW-1. While
some optical glass was made in France and England most of
it, especially the Barium types, came from the Schott works
in Dresden which was controlled by Zeiss.
The "rare earth" glasses, which have many desirable
optical properties, were developed at the National Bureau of
Standards in the U.S. in the mid-1930s and developed
commercially by Eastman Kodak. Kodak used it first in about
1940. I seem to have problems with names tonight so can't
pull up the two fellows from NBS who hold the patents for
rare earth glass. The range of index and dispersion of
these glasses helped to make very superior lenses. The only
problem was with thorium which is quite radio-active.
Unfortunately thorium imparts desirable optical properties.
It was used in some Kodak aerial lenses during WW-2 and
radiates enough to cause "browning" or staining of the
surrounding glass.
I really think its time to get some sleep now.
--
Richard Knoppow
Los Angeles
WB6KBL
dickburk@xxxxxxxxxxxxx
---
Rollei List
- Post to rollei_list@xxxxxxxxxxxxx
- Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe'
in the subject field OR by logging into www.freelists.org
- Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with
'unsubscribe' in the subject field OR by logging into www.freelists.org
- Online, searchable archives are available at
//www.freelists.org/archives/rollei_list
Other related posts:
