[LargeFormat] Double Protar Lens

[Clive Warren]

At 14:11 05/09/2003 -0700, Richard Knoppow wrote:

>----- Original Message -----
>From: "Clive Warren"
>Sent: Thursday, September 04, 2003 12:39 PM
huge snip
> > 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".
>
>    From my undated but c.1910 B&L catalogue this is a No.13
>Series VIIa Cells are both 16-1/8", combined focal length:
>9-1/4", at f/6.3.  Covers 6x1/2 x 8-1/2 at full aperture.
>This is an image circle of not quite 11 inches.
>    The maximum image circle is around 80 degrees at f/45
>(from experience, not the catalogue.) Individual cells have
>about 40degree coverage, they are f/12.5.
>   This catalogue shows only the "C" set.
>   Any Series VII Protar can be used with any other provided
>they are mechanically compatible and the ratio of focal
>lengths does not exceed about 1.5X
>   Stopped down the lens should cover 8x10 at around f/22 or
>f/32. The image circle at f/45 should be around 14 inches,
>maybe a bit more.
>---
>Richard Knoppow

Richard,

Thank you very much indeed for the information from your catalogue. I will 
have to wait for the lens to arrive to see the barrel size. It will 
probably be in a larger barrel as the 16 1/8" cell is part of a D Set. It 
sounds as though it will be a useful lens for 8x10.

The D cells could be grafted into a Betax #5 shutter or maybe a #4 using a 
sleeve or two. Will have to sit down with a ruler and check that out. The C 
set Krauss and Ross lenses (at least of some vintages) have the same cell 
thread rate and size so it may be that are a few more candidates for 
building up a set.

Cheers,
             Clive