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Suibuliu
Joined: 14 Jun 2002 Posts: 4 Location: Canada

Posted: Sat Jun 15, 2002 6:48 am Post subject: 


Hi,
I got, I believe, an Anniversary speed graphic 4X5 camera off ebay
today. Along with the camera is a Dogmar 1:4,5 F=18cm D.R.P lens from
C.P. Goerz Berlin, series number is 46882x (there is a matching number
in the rear group behind the lens board too.)
The lens is uncoated, and the aperature numbers are kind of strange,
the numbers are 4,5, 6,3, 9, 12,5, 18, 25, and 36. (not like the
numbers I am familiar with, such as f5.6, 8, 11, 16, 22, 32 and etc.)
Anyone knows any information about this lens? such as the year of lens
and its coverage (will it cover 4X5 or larger)? Is this a sharp lens?
Thanks,
Suibu


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Dan Fromm
Joined: 14 May 2001 Posts: 1914 Location: New Jersey

Posted: Sat Jun 15, 2002 1:26 pm Post subject: 


Quote: 
On 20020614 23:48, Suibuliu wrote:
Hi,
I got, I believe, an Anniversary speed graphic 4X5 camera off ebay
today. Along with the camera is a Dogmar 1:4,5 F=18cm D.R.P lens from
C.P. Goerz Berlin, series number is 46882x (there is a matching number
in the rear group behind the lens board too.)
The lens is uncoated, and the aperature numbers are kind of strange,
the numbers are 4,5, 6,3, 9, 12,5, 18, 25, and 36. (not like the
numbers I am familiar with, such as f5.6, 8, 11, 16, 22, 32 and etc.)
Anyone knows any information about this lens? such as the year of lens
and its coverage (will it cover 4X5 or larger)? Is this a sharp lens?
Thanks,
Suibu
 Can't help you with the lens, but the f stop #s are each midway between the numbers you're used to, e.g., f/4.5 is midway between f/4 and f/5.6. f/ #s are a geometric progression, each full stop is sqrt(2) times the previous one, e.g., 1, 1*sqrt(2), 2, 2*sqrt(2), ... Each half stop is sqrt(sqrt(2)) times the previous one, e.g., 1, sqrt(sqrt(2)), sqrt(2), ... , 4.0, 4.0 * sqrt(sqrt(2)).
Hope this helps,
Dan 

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Les
Joined: 09 May 2001 Posts: 2682 Location: Detroit, MI

Posted: Mon Aug 12, 2002 8:00 pm Post subject: 


In "A Handbook of Photography" these were called "continental stops". The Dogmar was the replacement of the Celor. Both are dialyte designed lenses, similar to the Artar.
You can almost double its focal lenght and lose a stop by using the lens withthe front element removed.
_________________ "In order to invent, you need a good imagination and a lot of junk" Thomas Edison 

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