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Dogmar 18cm/f4.5 lens information

 
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Suibuliu



Joined: 14 Jun 2002
Posts: 4
Location: Canada

PostPosted: Sat Jun 15, 2002 6:48 am    Post subject: Reply with quote

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 un-coated, 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: 1883
Location: New Jersey

PostPosted: Sat Jun 15, 2002 1:26 pm    Post subject: Reply with quote

Quote:

On 2002-06-14 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 un-coated, 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

PostPosted: Mon Aug 12, 2002 8:00 pm    Post subject: Reply with quote

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.

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