[LargeFormat] plastigmat lens

[Les Newcomer]

the patent that Richard mentions discusses the possibilities of 4 
element lenses, (no mention of lens names, as that would be limiting) 
with some positive and some negative elements and their positions.

 From this same patent Ed Bausch brought out the Unar.  Their was a 
codicil amending the patent when it was discovered that one of the their 
combinations turned out to be the Protar. The codicil acknowledged that 
Zeiss had the patent on that combination and they quickly backed away 
from it.

A few years later they brought out the PORTRAIT Plastigmat, and the 
Portrait Unar.  While the Portrait Plastigmat was a different animal 
entirely, the portrait unar was the same design with an expensive  
mechanism to shift the second and negative element back and forth.

Les
On Wednesday, August 21, 2002, at 10:51 PM, Richard Knoppow wrote:

> At 06:07 PM 08/21/2002 -0400, you wrote:
>> Mr. Warren, I have a copy from the B&L catalog that list the plastigmat
>> lenses available. It's my understanding that these were made as early 
>> as
>> 1900. If I recall, the front and rear elements were each made of 4 
>> glass
>> elements cemented together. They were like anastigmats in that either
>> the front or rear elements could be used separately. The plastigmat I 
>> am
>> interested in was code named by B&L by the name "Plastpox". This
>> particular lens was 4 inches in diameter (unmounted) and had a focal
>> length (both lens elements) of 26 inches (52 inch fl for individual
>> elements).  I'm interested because of research on an 11 ft. x 6 ft. x 5
>> ft. camera that was used to make 1.33 times life size negatives, from
>> which large contact prints (5 ft. x 30 in.) were then made. If you have
>> any information about the existence of this lens, I'd be glad to hear 
>> of
>> it.
>>
>> Thanks,
>>
>> Charles (Huntsville, AL)
>>
>>
>   FWIW, the patent for the Plastigmat is USP 660,747 (1900) issued to
> Edward Bausch.
>   The lens is listed in the 1907 B&L lens catalogue. One longer FL is
> listed, a 29-1/2 inch lens.
>   The only coverage data given is that the 26" lens will cover a 16x18 
> inch
> plate at f/6.8. Assuming it behaves like a Protar, which it resembles in
> general type, it should have significantly larger coverage at small 
> stops,
> up to perhaps 80degrees. Since a lens covers an image circle at 1:1 
> twice
> the diameter of its infinity coverage this lens would just about make it
> for the size format mentioned.
>   The single cells of convertibles have no larger image circles than the
> combined lens despite the nearly double focal length.
>   The catalogue does not list the FL of the individual cells but they
> should be around 1.8X the combined FL. Remember, the spacing between the
> cells must be taken into account in calculating the combined FL.
>   A slightly later (but undated) B&L catalogue no longer has the 
> Platigmat,
> perhaps because it was competing head to head with the Protar.
> ----
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@ix.netcom.com
>
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