[LargeFormat] Double Protar Lens

[LNphoto]

A pair of 16 1/16" make for a 9 1/4" focal length that covers 6x8 wide 
open and 8x10 at "smaller stops" usually f22

I gotta check other sources on the lettered sets.

Les

On Thursday, September 4, 2003, at 03:39  PM, Clive Warren wrote:

> At 7:20 pm -0400 1/9/03, LNphoto wrote:
> Huge Snip
>> According to my 1911 catalog, a pair of 11 3/16" cells give a 
>> combinded focal lenght of 6 3/8" @ f6.3 and covers 4 1/2 x 7 1/4. 
>> Something tells me in later years that was rounded to 5x7.    The 11 
>> 3/16" cell alone will cover 6x8 (whole plate) and has a back focus of 
>> 12 7/16".
>>
>> I have a couple of B&L double protars....enough to make a D set.  I 
>> also have C+ set from Zeiss.   While the glass may be similar, you 
>> have to remember these were made with "native" machines.... The Zeiss 
>> is metric through and through,  The B&L is Yankee.  The Ross may be 
>> "stricken" with Whitworth threads, so that tube may need different 
>> threads at one end than the other.
>>
>> Les
>
> Les and Richard,
>
> I seem to have become the target of used Protar dealers ;-)
>
> There is now another set winging its way towards sunny Bristol from 
> the caves of Mordor in the North.  This time it is again a set of same 
> focal length cells, Bausch & Lomb - Zeiss Protar Series VII Focus 16 
> 1/8" both front and rear cells.
>
> From what you have said, it seems that one of these would have formed 
> part of a D set? Presumably in a larger diameter barrel than the C 
> set. Perhaps your catalog has the info. for the combined focal 
> length..... would be great if the combined lens covers 8x10 however I 
> have the feeling that you are going to tell me that the combined FL is 
> around 8".
>
> It seems almost certain that the previous lens is a pair of 11 3/16" 
> cells as you suggested. The stops are marked in the Unified System 
> which caused me some confusion initially f:16 = f/16 and work from 
> there......
>
> Cheers,
>        Clive
>
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