[rollei_list] Coated Lenses
- From: Marc James Small <msmall@xxxxxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Thu, 10 Nov 2005 21:11:48 -0500
At 05:48 PM 11/10/05 -0800, Todd Belcher wrote:
>Actually, there is a 'unclean' uncoated lens that is okay - and that is
>when an uncoated lens acquires some tarnishing. H.D.Taylor, the
>inventor of the Cooke Triplet, noticed that old tarnished lenses had
>higher light transmission than newly pollished ones.
Hmm.
Todd, it is not quite that clean a matter. Harold Dennis Taylor indeed
noted that a mildly degraded surface on the lens sometimes improved image
quality by increasing contrast in the final image but he also noted that
this was a far less than universal condition and that additonal research
needed to be done: Taylor was, in the end, a consummate scholar of the
optical craft. (His papers are, I believe, being processed for publication
but I've not heard of the status of this for several years and I probably
should enquire, as there will be much of interest there.)
Taylor's observations led to work in several companies on this. Wollensak
and Kodak in the US, Ross in the UK, and Zeiss in Germany all involved
themselves heavily in the research on this during the 1920's and 1930's,
and all had a working vacuum-coating technique in operation by 1940.
However, Wollensak, Kodak, and Ross have never revealed their methodology
while Zeiss has done so, so they are generally credited with the scientific
priority on lens coatings.
Karl Bauer explained just how lens coatings could reduce contrast in his
PhD thesis in the early 1920's. Zeiss then assigned the development of a
commercial process to Alexander Smakula who combined the idea of using
fluoride coatings with an application by vacuum coating to produce the "T"
method in 1935. This was patented in openly in 1939 and so Zeiss
controlled the rights until 1959, and they only allowed a very few firms --
Schneider, Voigtländer, and possibly Kilfitt -- to join in the pool of
those permitted to employ the technique.
Dr Karl Bauer was diverted frm scientific research when he was sent by the
boys at the Jena Rest Home to run Carl Zeiss, USA, in 1938. He ran it
then, and he continued to run it after it was seized by the US government
in 1942, and he continued to run it by being politically blind: after the
war, he did business with Carl Zeiss Jena and Zeiss Ikon VEB along with
Carl Zeiss (Oberkochen) and Zeiss Ikon (Stuttgart). He made money and the
US government so appreciated this that they refused to allow the Gnomes of
Heidenheim to repurchase Carl Zeiss, USA, until he had earned his
retirement, which occurred in 1960.
Dr Alexander Smakula was brought to the US by the American military after
the War, and ended his career as Chairman of the Physics Department at MIT.
But, again, a clean uncoated lens properly shielded from ambient light will
work every bit as well as will a coated or multi-coated lens.
Marc
msmall@xxxxxxxxxxxx
Cha robh bàs fir gun ghràs fir!
NEW FAX NUMBER: +540-343-8505
---
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:
